[kevm14]

I find the original WM5-style PIE to be just about totally useless as a browser. IE6 is a HUGE improvement. It has kinetic scrolling (though choppy) and if you double tap, it zooms in correctly on what you want to read. Skyfire is also pretty terrible (bad scrolling, bad zooming, not true VGA) UNLESS you need server-side rendering (I don't). Iris has some slickness inherent to Webkit and scrolls the smoothest of any I've seen but doesn't reformat the margins of text when you zoom in to read. I'd have to say Opera would be my pick if I was left with only one. Scrolling works well (not as smooth as Iris though), the adaptive zoom is by far the best, dynamically changing margins to fit your new zoom level.

Here's something I just put together. This is performance in MightyROM 5 on my Touch Pro:
Opera opens in 4 seconds displaying google.com mobile in 7.
Iris opens in 3 seconds displaying google.com mobile in 6.
PIE6 opens in 3 seconds displaying google.com mobile in 5.

None of these significantly differ so I choose by function after loading.