Thinking about getting the Android-powered—and 3G-enabled—T-Mobile G1? Here's a tip: Before you buy, make sure to check T-Mobile's coverage map to see whether you live in a 3G coverage area.

I just got an e-mail from a T-Mobile spokesperson who notes that the carrier just updated its 3G coverage map; just plug in your address to see if your neighborhood is bathed in speedy HSDPA goodness. The new map is pretty detailed—down to the street level, handy for pinpointing 3G dead zones within otherwise covered cities. (The darker area represents 3G coverage; the lighter area is EDGE-only.)

T-Mobile's 3G network just went live in May, and it's still relatively limited compared to the other big carriers. By next week—when the G1 is set to arrive in stores—only about 21 markets (comprising 92 cities; you can check the full list right here) will have 3G access through T-Mobile, compared to more than 200 markets each for AT&T, Sprint, and Verizon Wireless. [Update (10/21): The latest word is that T-Mobile has 95 cities set with 3G coverage; the three latest cities are Memphis, Tenn.; Clearwater, Fla.; and Tampa, Fla.]

Now, keep in mind that the new G1 (check out my full review) will still work even if you don't live in a 3G coverage area—T-Mobile offers EDGE data access (think dial-up speed) for most of the country, and the G1 will also connect to any Wi-Fi hotspot.

That said, such features as Google Maps, Web browsing, and full-track music downloads may slow to a crawl if you're only connected to T-Mobile's EDGE network—just ask anyone with the EDGE-only iPhone on AT&T. Consider yourself warned.

Related:
T-Mobile 3G coverage map