I have been a very happy customer of T-Mobile's for six years. I recently bought the MDA after my Sidekick II got stolen. I liked the sleeker design better as well as the list of features. I regret the move. The SK II is faster, much easier and more intuitive (and fun) to use. Starting with the keyboard.- the SK II has four rows, the MDA only three. The SK II offers an additional row of keys with numbers, a separate `@'-key right were it belongs, and two `shift'-keys (one left , the other one right to the space bar). The MDA? Only one 'shift' key on the left.The MDA's user interface is a mess. The same function can be found on totally different keys depending on the menu/screen you are in. For example, be default the function key on the right gets you to the `contacts' list when you are in the main menu. When you get to the dial pad, the `contact' menu needs to be accessed via the left function key. When using the phone, the `contacts' button is on neither function key but on the touch screen.Other weaknesses: For some windows you actually need the stylus to close them, others close by pressing the `hang-up' button twice. The speakers are weak. Virtually all comparable phones I know have better sound quality. The touch screen sometimes does not work (maybe because the phone is busy with something else and can not query the screen?), so that when I want to use the phone, I need to enter my PIN using the keyboard (which does not have a dedicated numbers row). You cannot assign ring tones to callers - a very basic feature even found in cheap phones. I also believe the email functions of th SK II to be much faster. I would get emails almost immediately after they were received by my mail server. With the MDA it takes up to hours, same for sending. Even text messages sometimes arrive 2 hours late. Never happened to me with the SK II.I heard that the Sidekick III will come out on July 10. I will switch in that day!