I spend a lot of time in my head.
Usually when I'm talking to someone, it feels forced and I only really pay 50% attention to them at best, I listen for a bit and scatter. I also make really poor eye contact.
I miss body language queues, mostly the micro-expressions, simply because I'm not really paying attention.
I'll usually always have a self-critical monolog running in my mind, often causing me to lose focus on whatever it is I'm doing. If I'm talking to someone I can sometimes just stop talking as I forget what I was saying, as the other voice in my head grabbed too much control.
I often lose things by putting them down somewhere and just not registering I did so and/or remembering where I put them.
I make a lot of careless mistakes at work, particularly when repetitive tasks are involved. Even when I actively try to make it not happen, it just keeps happening.
I am a very erratic worker. I'll sometimes do a big chunk of work, almost always on something I'm truly interested in. More often then not, I'll procrastinate and put things off until the pressure of consequences builds up so that I do it. Usually when I have only just enough time left. Every now and then I underestimate the time required....
I'm very prone to getting suddenly interested in a topic/project and have an initial flurry of activity and then the interest can rapidly fall. Usually when I have to do a bunch of procedural stuff to actually make it happen. I've rarely finished projects.
I have a strong tendency to take the immediate reward over a future reward. This makes choosing to do things that improve my life hard to do.
I have poor memory for names, places and discrete factual information.
I have a great memory for concepts and abstract ideas.
I'm a bit sluggish at switching tasks, so moving my attention from one task to another. I will often lose bits of information when I do so and when I switch back have to figure out some stuff again.
When I get excited, I start getting impulsive tendencies of talking over people and babbling my ideas in a semi-coherent fashion.

It's not easy to arrange my thoughts into a logical order and explain my ideas and reasoning to people in oral communication. I often forget parts, explain something, then realise it doesn't make sense without explain something else and it is a bit of a mess. With periods of sudden loss of words, usually because of those pesky other thoughts.

My ability to hold numbers in my head and do simple maths is a bit shit. I totally understand the concepts and can do complex written maths (not complex like a mathematics expert lol). I just can't do much in my head, that many other people seem to be almost fluent in. I'm 35 and still use my fingers to count sometimes lol.
I get irritated and frustrated easily, particularly towards the evening and/or when people interrupt me when I'm pleasantly monologging away in my head.
A fairly distinct lake of empathy. I could think about and get a generalised understanding of peoples situation, but I wouldn't feel it. Spontaneous empathy was a very rare occurrence for me. It was something I really wanted more of.

There are more things. It is also all wrapped around being on the extreme end of introversion and almost always having a streaming monolog going in my head that often interferes with what I'm doing.

It causes significant problems at home. I have a partner and 2 young daughters and it's rough on them when I get the shits so easily and I just can't seem to pull my shit together enough to be a true partner of my spouse. We often fall into a parent-child dynamic.
It has cost me promotions at work at multiple work places, particularly the high level of careless mistakes. Poor networking from crappy socializing ability combined with poor follow through of promised non-critical tasks has also had a solid impact to not getting anywhere.

I failed uni a couple of times, partly due to the above symptoms and partly due to being rather depressed at the time (due to consequences of my symptoms).
My school results were very average, with the occasional good grade when I was interested. My report cards peppered over and over with 'easily distracted, has potential, needs to apply himself, etc'.

I had a constantly recurring thought that I was different but not sure why, for most of my life.
When it came to introversion, I don't want to be introverted all the time. I can't not be without the help of meds. I hope this is part of my compensatory personality to hide/mask ADHD symptoms and reduce socially derived anxiety. I remember as a child I was more out going and extroverted, so that gives me hope that I can attain that without meds again.

Oh. I also played shit tons of computer games. Mostly competitive games.
Also, whilst I could identify most of these issues prior to diagnosis and medication, I couldn't fix them. In some cases I knew what to do, what the correct course of action is, but I just couldn't do it. Therapy helped with my initial depression, but as had little impact on the above. To the great disappointment to my partner, over and over and over.

I was diagnosed this year.

edit: OH, also there is butt loads of emotional turmoil, so much that I sort of became numb to it. When I think back now, I realise that most of my behaviours were thoroughly emotionally driven. What I was missing, and still am to a lesser degree, was emotional control. I longed for it even.

edit 2: OH OH I also am really disorgansied and have trouble organising things in a logical way, to the point where I've somehow managed to position myself in life where I have to so very little of it. My partner has taken a large burden of that, which isn't good for a solid relationship.
This applies to both my inner life and outer life. So I have a messy desk, messy cloths, messy filesystem on my computer, etc. My memory is also similarly messy.

Gees, this is a long post, but you asked!

edit 3:
The good news, for me at least, is that my medication has had solid improvements on many of my core symptoms. Emotional control is better, which leads to a range of improvements to the above. Particularly making better decisions (fruit over chocolate is, for some reason, one that sticks out for me. I ate a lot of chocolate, a lot.).
It's easier to accept delayed rewards over immediate rewards, again helps to make better decisions.
I can sit with my daughters for much longer periods of time without losing too much attention. A father who isn't present with their children isn't a great thing to me, particularly when you know you aren't and can't do anything about it..
It seems with better emotional control, I've got more room to feel spontaneous empathy. This has been a bit odd, I see/hear random people on the street having a problem and I feel a solid impulse to help. It's kind of new to me.

Sadly and confrontationally (internal) I can feel many of the benefits from medication slip as the medication wears off towards the end of the day. I hope over time, I can enact a range of habits that will help mitigate this effect. It's sad that I need to rely on medication to be a better me, the me I aim to be.