Inquire among your friends who is on TM and invite them over to your home for drinks. You would hate to discover that your new apartment is one street into a dead zone. I used to have Sprint and the signal would gradually drop to zero as I neared my home. Same as Rick with ATT a phone with no signal at my home (which is also currently my office) is worthless.
Initially I rooted my ATT Captivate so I could remove ATT bloat apps. Then I discovered XDA and have been running a custom ROM for nearly 2 years now. Fixed all the crap that ATT broke/disabled/removed. Light years better performance and battery life. Suck it ATT.