For designers, just including a JS file that does the compiling on the fly seems why LESS gets more love from that group. And also that Twitter Bootstrap uses it as default (although there are SASS ports of Bootstrap).

For beginners/designers to the whole precompiling CSS scene, setting up Ruby for the SASS/Compass toolchain could possibly be daunting. Although there are nice GUI alternatives: http://mac.appstorm.net/roundups/internet-roundup/5-mac-apps...

However I agree with other comments that it seems there are more tools/frameworks built on SASS (with Compass), that make it more appealing to me.