I'm with the rest on this one.
I'm a CS5 user that was in the same boat as you just a few months back.. I have photoshop CS5, but is Lightroom something worth getting. Short answer is "YES"
In my case, The ability to quickly move between photos and albums while adding adjustments is worth the cost alone. Photoshop made me load individual photos, one at a time.
If you shoot in RAW it's even better with the ability to go back and fix things like WB (and other things.. I'm still learning
Russell had a great suggestion as well. Adobe gives you a 30day trial FREE!, you should take advantage of that.