Is Fallout New Vegas Ultimate Edition for the Playstation 3 worth 40$ ?
Does the glitchiness get so bad after ahwile that you cannot complete every quest and cannot explore every inch in one playthrough ?
What patch does it come with ?

If you have another method of playing it (360 & PC), get one of those, but if PS3 is your only option, I'd say go for it.

Typically, PS3 users with the ultimate edition can only complete a good portion of the main game (enough, is all I can say. Hard to describe, but I doubt you'd feel limited there) and two of the four DLCs. Sadly it DOES suffer from the same slow-down issues that all other Bethesda titles share.

If you can get it on Xbox or PC, get it on one of them instead. Even if you'd be playing on the PC with minimum settings, buy it for PC. Otherwise, it's definitely a game worth buying, but be aware you probably won't be able to explore every DLC on a single character.
The PS3 tech support forum is also worth checking out. Every so often someone posts a workaround with fairly good reception, though I'm not a PS3 user myself so I couldn't personally tell you how reliable they are.