I stayed at the GC with my kids a few months back. Had always wanted to do it, always envied the guests who could wake up, step outside their hotel, be in the parks. How cool!
We liked it and we're glad we did it. But for the cash, it really ended up not being worth it for us. Perhaps if my kids were older (they were 4 and 6 at the time) it would make sense: eat at the nicer places, use the spa and gym, hit the parks, come back for a nap,etc. So for older kids or if you are going just with a significant other or just another adult I think GC makes good sense.
If you are looking for a more relaxing, highly convenient place to stay and you want to spend the extra cash, I say go for it. We had a really nice time there and there is no doubt it's a top flight hotel. But since most of our time- 95% of it- was spent either sleeping or in the parks, the extra cost was not justified.
We're going to DLR this weekend in fact and are back to our old standby: The Candy Cane Inn. For us- because we pretty much live in the parks and then sleep- it's a perfect deal. But again, depending on the kind of trip you are after, GC could be the perfect fit.
Spidey