I'm also curious about this. The problem I have with the language button is that when I tap it accidentally, it takes a second or two for the "language selection" dialog to popup... With the capslock key, I didn't really have that problem. If I tapped it on accident, I could untap it without missing a beat. As it stands, I have to pause typing for a little bit until the dialog pops up, just so I can close it. It gets really annoying. Alternatively, if I could just disable that button altogether, that would be fine because I don't even use an alternative language...