Me, perosnally.
vBulletin has made it harder and harder for us coders/designers to make things new without making us spend wayyy to many hours on simple stuff.
I am pretty much giving up on vBulletin myself -- I shouldn't have to redo my skin every .0.1 upgrade and shouldn't take 20 hours to make a simple widget that pulls universal data (skinning the widget I mean)
TL

R -- vBulletin is making it harder and harder and the pro's and easier/easier to do stupid stuff for the noobies with 0 code experience