Each Motorola ATRIX owner has seen their fair share of ups and downs, the biggest down of all perhaps being the lack of up(load speeds), as the ATRIX 4G doesn't have HSUPA support out of the box. AT&T has promised a fix for this and we've even seen phantom updates arise to fix the issue. As always, though, when carriers and manufacturers fail us, who do we look to? XDA, of course! This occasion is no different, and user dew.man has come through.
Basically, all you need to do is flash dew.man's modified 1.87 baseband radio using RSD Lite... and that's it. If, for some reason, you experience issues after the flash, then he has also included a current, stock baseband so you can flash back if need be.
Zack over at Droid Matters has posted full instructions on how to flash this, so check that out if you're not sure what to do. Here are a couple of before and after (respectively) screenshots that he took to give you an idea of what to expect:
As always, hit the source thread if you experience any issues.
Best of luck!