TM506 from Sony Ericsson is now on sale, marking the first time that T-Mobile has openly and proudly admitted that a handset in its lineup can actually support 3G -- despite the fact that they've had such gear for over a year now. Why the big secret? Until now, T-Mobile's 3G network has been undergoing pretty much the softest soft launch in mobile history, and only now are enough markets starting to come on board to make the whole thing worthwhile. For what it's worth, every previous 3G handset on the carrier has merely rocked UMTS, so the TM506 becomes its first HSDPA-equipped piece while also offering up a 2-megapixel cam, TeleNav navigation, and stereo Bluetooth. As of this writing it's still showing "Coming Soon" on the site, but we're hearing that it'll be available today for $79.99 after rebate on contract.