I absolutely love the customisation in this game. You can literally spend hours just creating tattoos, logos, ingame music, customising clothes and cars and creating your character to be exactly what you want them to be. The level of freedom with the tools is just incredible.
I think the main problem with the game is that everyone will automatically compare it to GTA and it isn't quite as polished as GTA. The driving style is probably one of the biggest let down for me, but you can get used to it after a while. The FPS element isn't terrible but could do with some work and a bit of balancing here and there.
The mission content is a bit repetitive and I think that is probably going to be their main issue. It is literally go here, press f, go back to here, collect this, drop it off here...over and over again.
If they work on adding more content to the gameplay I think it could definately be a great MMO.