If you're in the market for a myTouch 3G, our advice would be to wait until the myTouch 3G 1.2 becomes official and then decide which one to buy. Even though T-Mobile is going to drop the price of the original myTouch 3G to $99.99 on February 10th, the myTouch 3G 1.2 might be a better option in the long run.
The rumored updates for the myTouch 3G 1.2 are the 3.5mm headphone jack, Swype keyboard, and increased memory. The first two upgrades might not affect you but having increased memory may give a performance boost to the myTouch and maybe even allow it to cleanly run something like HTC Sense. And plus, $99 for a myTouch 3G is hardly the best deal in town.