Helga, since you're in NY, check out Bell Atlantic. I've had no problems with their service, and they're running a special for the next few days only. 300 minutes for $29.95/month, local calling area is Boston to DC.
I've had my phone for a few months, and no problems, even on NJ Transit trains. My girlfriend had AT&T, and it was horrible. Constantly dropping connections, lousy quality. My company's BA rep said that AT&T vastly oversold their network and couldn't provide service steady enough to meet the demand. My girlfriend's service with AT&T corroborates what he said.
Yesterday, she switched to BA with the special they're running (they've been advertising in all of the big NY papers), and she loves it so far. Marked difference in the sound quality, and no more dropped connections.
A few of my friends have Sprint also, and they like it. I heard some not so great things about Sprint a while back, but my friends have reported no problems recently.
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From another BBS:
"hmm... Cyrix III, huh? You can put syrup on sh*t, but that don't make it pancakes."