Well, it seems that could be fixed by only having the phone vibrate for the first message. Even if I'm using the phone, I don't really need it to vibrate all the time...
There are lots of things that Skype "could" fix. The point that I am hearing from the GP is that they do not CHOOSE to fix them. You should see the Skype 5 beta for Windows. What a UI cluster that thing is, and has been for quite some time now.
And I just tried Skype for my HTC Desire on 2.1 and yikes, he's right: it's a usability nightmare.