I doubt there is a videoediting application which supports UI scaling today, but from what i heard Adobe are working on adding support for highresolution displays, if it's not taken care of already.
/ Magnus
Adobe implemented a 200% scaling (fixed) for Photoshop. When I tried Premiere, no scaling possible.
How sophisticated do I need? Well, I have used FCP on my Mac. Obviously I did not use all of the features, but advanced modification of clips, timing, stabilization, batch clip rework etc. So something between the MUI s/w and Premiere ideally.
I do lot of diving and need to post process the clips for color correction at various depth levels, smoothen shakes and want to have control over timings. This is actually what prevents me giving my MBP away, but I really want to use the SP3 because I love the form factor and transportability of the system.
Corel Video Studio does not even start on my system, so I cannot evaluate.
Magix is ugly, I don't like it too much. Cyberlink ... not tested yet.