T-Mobile just released their 2.26 update for the MDA on their official site. If you go to your my.t-mobile.com account, log in, click "support for MDA", then click on "System Upgrade", you'll be taken to the download site for their new upgrade. The link didn't show up for me last night, but it shows up now. Or, you can just click the direct link we have below.
This update will erase all your data on the MDA, so you should back up your contacts and data first before upgrading. Be careful when you update, since you're writing some low level stuff to the phone, and you may brick it if something goes wrong in the update process.