Why Is AT&T 3G Data So Unstable?

It’s on and it’s off, for no apparent reason. That’s how my AT&T 3G data service is in NYC. I have 2 devices, an iPad and a Blackberry, both on AT&T with 3G and very spotty service. I sometimes get a very reliable connection with around 180KB+ down, and other times I can barely get connected to the Internet. This happens in both my apartment and at the office, not when I’m moving around. So it’s the same place and probably same cell towers, but service is still unpredictable. The bars doesn’t seem to matter, I can have full bars and very bad data service or just a few bars with very good data service. It’s just unpredictable, and it drives me nuts. I also have a X10 Mini Pro on T-Mobile EDGE, which I find much more predictable. While on T-Mobile EDGE with full bars I get around 20-25KB down, and it’s slower with less bars. Slow and predictable I can deal with, but not fast and unpredictable where I never know whether it’ll work or not. Hopefully the Verizon iPhone launch will lighten the load on AT&T.