I'm having good luck with MaxCDN. I wouldn't say performance exploded, but it's well worth the $40 a year I pay to have my css, js, and images uploaded to their thing. It's all automatic after the install.
Without vbseo I've not tried it, but that's on my list today as I just switched to dbseo. Here's a super quick method to utilize a CDN in vbulletin.
http://www.cdn4cms.com/vbulletin-cdn...ment-variable/
Brandon