Yep.  And even beyond that, it matter what VST/VSTi plug-ins you use in a given host!  Some of the DAW-Bench tests running Nuendo/Cubase show a clear improvement with HT=On (more total threads, but less "work" gets done per thread).  However, my own projects (which differ drastically from the DAW Bench stuff) seem to prefer HT=Off (more CPU power per thread, but less overall threads).  Kind of like the old "fast 3.33GHz dual core or slower 2.4GHz quad core" debates that die-hard Gamers had when C2Q's first came out :-)

Also, if you are into overclocking, HT=Off will lower temps and allow a higher resultant CPU clock.  For me, HT=Off is a no-brainer due to my specific use of my DAW and software as a whole.

Not likely to make a major difference - just try it out...

Regards
Daniel Fuchs
RME