I'd be VERY interested to see what kind of custom modding can be done on commonly available LCDs to remove the bezel and make a very slim bezel eyefinity setup.
Not something we'd all try, especially without some good guidance on what to expect inside the things, and probably one or two good...
I would totally go for a 5770. From benchmarks, it seems powerful enough for most apps & games, and for the price and forward compatibility, it's great. Being last gen and for its price, I just don't think the 4870 is a good choice.