I tried that as a replacement for the Sidekick keyboard and it just isn't the same. The physical keys on the sidekick had really nice action and were separated sufficiently to avoid hitting the wrong keys. This one, they keys are too close together and they're arranged in a grid, not like a traditional qwerty keyboard.
It's been a while since I had to give up my Sidekick LX. Microsoft shut down the servers that made the web browsing possible. I strongly considered keeping the account just so I could use my Sidekick for messaging with its fantastic keyboard, but ended up switching to an iPhone. The iPhone is great in many ways but I really don't like the virtual keyboard.