I finally got nsd 3.5.1 installed. The only hurdle was I didn't want to have two different tcl installs, so I had to build my own RPM to replace the old. What a PITA. Too bad none of the source-based distros have a decent installer yet.
The big motivation for me was 3.3.1+ad13 would reliably crash every 20-80k pages served. This tended to piss users off since carnage blender is so update-intensive I have to aggressively buffer writes to the database to keep up with demand. (I thought it was a hardware issue, but after getting a new server I had the same problem.) 3.5.1 has served over 600k pages now w/o a hiccup, so it very much looks like the particular bug(s) causing this got fixed.