Hi Shane,
1) The current HTML product doesn't offer scripting and tab merging. I would stay away from it and wait for the next Personas release later this year which will be completely HTML based, built into the Webgui and get rid of the Silverlight dependency. Should also improve performance.
2) Definitely SP2 however you would have to patch the kernel to at least 228 as described here:
Announcing SAP Screen Personas 2.0 Service Pack 2 (SP2); also Personas 1.0 SP4
3) The main difference is the HTML product version but as I said, I wouldn't embark on implementing that right now.
You could also stay with Personas 1.0 and install SP4. This is equivalent to 2.0 SP2 (with the exception of the HTML product version which is not present in ver. 1.0), then upgrade to ver. 3.0 once it becomes available.