ARGH! Why can’t the same software run on everything?!
Of course as developers we know why (the lowest common denominator problem, patents, turf wars), and can point out failed attempts to change this (cough Java), but sometimes it helps to see a less technically proficient user's take on what we've developed as software folk.
I suppose that's where web applications have the potential to shine, provided we move enough people onto standards compliant browsers. I very much doubt we'll ever have a consensus on a standardised desktop API, though I suppose Win32 came awfully close with a de facto one ;).