Nick Isherwood the main one would be that of the transition deal in which we will keep paying into the EU which will only end when both the UK and the EU have agreed on future trade arrangements.  As a member state you have the option to trigger article 50 and leave, this transition period has no arrangement to pull out and could potentially keep us within the union until 2099.
I also consider it treasonous and incredibly stupid to put a hard border down the irish sea, northern ireland is part of the UK and this would be leaving them under the juristiction of brussles and dublin.  Its absolutely unacceptable and may well lead to the troubles returning or worse still break up of the united kingdom, as the SNP have said if NI has got that arrangement (which the DUP have made very clear they dont want) then they want it too.
Not to mention the ridiculous sum of AT LEAST 39 billion as a divorce settlement, i have alway been a avid brexiteer but this brexit (I use the term very loosely because this isnt brexit at all) is not only pointless, but stupid and dangerous.
Trying to negotiate with the EU whilst being a member state is a complete waste of time, and they have already said the re-negotiation of this deal is out of the question as a deal has already been agreed.
This is why May has to go, because shes the one that agreed to it knowing full well hardly anyone else would