Seems that with handheld devices on the rise, one has to start taking them into account more and drop IE6 instead.
With that in mind, it has come to my attention that c
following link should help. To make website like a nativeapp, jQuery plays amazing role
http://blog.2partsmagic.com/2012/07/developing-web-application-ipad-android-tablet/
I can answer the conversion rate/business viability part of your question.
I had the chance to see Omniture numbers for some very, very big ecommerce interests and the answer is that conversion can be somewhat less, somewhat more, or about the same. There was a pretty good amount of variance depending on the device and the seller's site.
It's what you'd expect though, I think. The quality of the mobile/tablet experience varies a lot right now depending on how well each business optimized for mobile (and for which mobile devices). I think conversion varies a lot as a result.
You've just asked a lot of questions I've been asking myself recently. I can't give great answers yet as I'm still researching and exploring. but here are some useful links.
I hope this is at least a little helpful.