As with others, mine was set to the "epc" APN out of the box. When I ran into some of the issues with YouTube videos hanging, I read a couple of posts suggesting that I change to the old wap.voicestream.com APN -- and considered it. But while I let the thought percolate a bit, I made a point of using YouTube's WAP interface (I had been using the regular site), and for whatever reason, I now found that I could browse and watch a couple of dozen videos with absolutely no issue at all -- still using the new "epc" APN.
I'd be interested in seeing if we could get real info about the differences. Anyway - mine seems to be working fine now, using the "epc" APN.