Woohoo. Great timing. Just started re-doing this to learn 3.2. Do you inject bootstrap into the app or use Seyhunak's twitter-bootstrap-rails gem?
The main exception to this was for 2.0, which had a separate branch for a while so that people could still use bootstrap-sass while updating their application to the new syntax. When 2.0 was merged into master, since it had been under such heavy development I reconverted the entire codebase.
There are a few quirks with the conversion from Less to SCSS, but these tend to be few and far between, and are usually down to me missing a variable somewhere. The main one is the use of namespaced mixins[1]. SCSS doesn't support this, so I have to prefix/suffix the namespace to each mixin within the namespace. Aside from that, and method names/variable notation, there (appears to be, can't speak authoritatively since I haven't really used Less) little difference between the two.