I just made a switch myself over to AT&T...first time with them. I'm taking a whack at their nebulous 7500 Starwood pts deal. I figure it's worth a shot.
Earlier this year, around January, I signed on with Sprint for the 20,000 miles on NW. They credited me 5000 miles twice during the first quarter, then another 5000 a couple months later, and finally the last 5000 just a few weeks ago in September. So it took me about 9 months to collect the booty. Without even calling or hassling over it...wow!
Prior to that it was MCI...originally a 10,000 AA bonus...then a short time with Sprint, then back to MCI as they offered me a whopping 25,000 AA miles to come back.
Have had fairly good luck in this arena...only hope is that AT&T comes through with my Starwood points on this current offer (not so sure).
Best of luck - DS