Level 40 leves could be soloed for ~10k+ exp a run solo for a while now. The added exp sounds nice for people not in a party. For the most part a few of the new/returning people in my linkshells have been doing leves to level up to SH runs.
While everyone is talking about PLing breaking the game, and there are no parties, I know a few people who are using the leve system to get through levels at a decent speed (at least they find it acceptable). And I used it while finishing off quite a few of my jobs (mostly duoing battle leves, or soloing grand company leves). The rewards aren't bad, and the exp is rather nice (and if you use them to build up seals, then go on a level 50 run, you get 15+k exp for completing one of those faction leves, not counting mob exp).
So, yeah, if you are having troubles finding a party, go out burn a couple leves, and while the exp gained for leve completion is scaled (low level leves give less exp for completion), the mob exp tends to be better at lower levels (probably a placebo effect from having less exp needed per level) then higher levels.