thal, thanks so much!
I'll dedicate my Schubert-X dabbling to you when I can upload something (well, this might be more a blame than an honour, depending on my playing...

).
Looking at op. 90/1, the Schubert-Liszt Impromptus seem to be only "normal" editions. There are some passages where Liszt adds an own voice for notes that were only noted as accompaniment by Schubert. But these are very minor changes. I guess it will be the same with the other Impromptus.
The Leschetiky also comes with only slight modifications to the original Moment Musical. (The Godowsky in contrast is a huge departure from the original
The Brahms is a (almost) literal change of left and right hand, similar to the Wuhrer edition of the Chopin etudes, for example.
I agree with the popularity of Schubert among transcribers, but the bulk of the transcription work seems to have been done on the Lieder. I was wondering if there are any interesting transcriptions/paraphrases of his original solo piano works around, but it looks like the Godowsky is by far the most interesting.
Have you seen/heard any of the stuff you mentioned in copyrighted? Is it worth buying?
Again, thanks a lot!!!
-Tobias
P.S. The Czerny variations op. 12 on the Waltz are a good piece... I mentioned the Lisitsa video on Youtube in another thread, it's worth watching.