Hello,
just for curiosity I compiled a Release version of explorer using the current Wine shell32/comctl32 implementation. You can get it at http://www.sky.franken.de/explorer/explorer-wine.zip.
...and what do you guess? This version feels reasonable faster while browsing the start menu than using the shell32.dll shipped with Windows XP!
Sure - we are currently not yet reading all those registry entries we should to determine the correct icons to display. Also Wine's shell32 does not yet support things like control panel and recycle bin. But looking into the supported start menu folders I can't see any substantial missing functionality comparing the two versions.
Merry Christmas!