I've only had the chance to play the full game on a limited basis, didn't seem to differ much from the demo; but on the whole was fun.
It is extremely GTA-ish, but not to compare it to the GTA3-Series (which I honestly only completed cause I started each one) as personally found them to be crap story-driven drivel.
Has more of the classic GTA feel about it, more back to basics in terms of what you were doing. Obviously though in a 3D environment with a cheesy story, and super-powers.
When I get home will probably pay through it after I complete FFXII.. cause just too addicted to that game through'n'through.
As for Gears, I'm totally with those who felt Single Player was boring after the first time through (which takes about 3-5hrs depending on how much you rush it). After that, on you're own it does really loose it's luster. Co-op and Online is pretty awesome and fun though.. very similar experience to Halo cause it's just a laugh from the get go.
Totally looking forward to the next Gears, and Halo
This said, this is comming from someone who still tends to have a habbit of playing on Viva Pinata quite a bit. Only a few pinata to go, then I'll have them all.. and can get down to the serious business of going after my final few achiements.