JKurz,
I also am in the same boat as you.
I have recently gone to sitting on an excersise ball at work. After a few hours it's quite a workout!
The biggest issue here is getting past your idiot co-workers/buddies who harrass you about it, and all the dumb jokes that go on for the first couple of weeks.
It does make a difference and increases your core-strength which will help you with your lifts alot as you'll start to recruit your core muscle groups to acheive your heavy lifts.
I've actually been flat benching off the ball now for a few months and I feel I could easilly...easilly lift alot more off the static fixed bench now than I ever could before. Try balancing 260+ lbs over your face/chest while you're balancing the rest of your body with a ball between your shoulders....!!!!!!! Then go load up 350 lbs on the regular bench.
I would feel very, very, very nervous if I did that anywhere but a safety cage!
Going on about the ball more, and likely to a tiresome degree, when I get harrassed or laughed at for using the ball to bench (or other stuff), I just pick some medium wieght dumbell or plates and offer the person to try it (smartass!). It's quite funny cause they realize immediately "HOLY SHIT! I can barely hang on to this shittly little dumbell/barbell". Then of course I add my usual weight back to the bar, or grab my usual dumbell and after that, no harassment, just respect...LOL!