The short answer is "not very well". I use SPB Mobile Shell 3 and wallet. I need to exit the apps before I fire up my redfly. They don't interfere, but you really can't use them. That doesn't stop me from using the software, I really like the way it works.
Yeah, you won't like it with the Palm Treo Pro and it's 320x320 screen (it doesn't scale right and will sometimes really slow down the phone and you have to to a soft reset).
However any phone like the Touch Pro or Diamond with a 640x480 or 800x480 screen works well with SPB Mobile Shell 3. SPB hard codes the resolution (it doesn't scale) but luckily it works on the REDFLY since the REDFLY has a 800x480 display.
There's sort of a work around with the Palm Treo Pro that I've used. SPB Mobile Shell 3 has a menu/option button in the bottom right corner. If you press it, one of the options allows you to immediately switch to your normal Today Screen. Once you're on the regular Today Screen, then you can connect to the REDFLY.
It's not the best work around; if you forget to do it before connecting to the REDFLY you usually lock up or slow down the phone and have to do a soft reset. And sometimes it messes up the phone even if you remember to do it right (but a soft reset always fixes the issue).
You can install the SBP trial to play around and see if you are OK with the hassle of that work around. I ended up just uninstalling it from my Treo Pro because it wasn't worth the hassle. Too bad, I really like SPB Mobile Shell 3.
One other issue with the new Spb products is that fact they are made to scroll with finger flicks. It is damn near impossible to replicate the motion with the mouse. I'm finding the same kind of issue with my Omnia, it wants to flick and scroll rather than use the scroll bars.