I have used this mod countless times, especially in game development. It has sped up tasks considerably and helped me a ton. I used it to create various structures and trees in MineClone 2, Lazarr! Glitch and Repixture.
During the development of Glitch, I have felt one of its biggest shortcomings is usability. Typing in chat commands all the time gets tedious and time-comsuming very quickly, especially if you want to do many complex operations in row. The worst part is setting pos1 and pos2 because you have first fly to these places (using mouse and keyboard) and then type in the commands. This part is always the most time-consuming.
Unfortunately, WorldEdit GUI only works in combination with selected games/mods for now.
I wish one day WorldEdit usability gets seriously improved because that area still needs work IMHO.
That having said, it's still a recommendation because it's still a big improvement over having nothing at all. Without WorldEdit, productivity would slow down to a crawl, so that cannot be understated as well. Still a good mod/modpack overall.