Hi Russ,
I am assuming that the output is pretty similar to the 20D which I owned.. I was never really quite satisfied with the 'on-board" black and white, (although I was really happy with the idea) and now do all my conversions in Photoshop using a plug-in from Theimagefactory called Convert B/W Pro.. It does a very good job of simulating a traditional dark room in terms of control, contrast, film types etc... The advantage is that you can shoot Raw and then do conversions when you download to your PC. I can see the image change as I play with the settings, colour filters, exposure and contrast.. It feels like my wet darkroom again, only less claustrophobic and I can do it during the day! :-)
Now that I have my 5D I have not bothered with picture styles as I only work in Raw, and leave the JPeg conversion for when I''ve finished manipulating the picture and am ready to print. I will as a matter of course shoot a few shots in B&W in-camera and report back.. if there is a significant improvement I will let you know.. However I am already so happy with my plug-in and the after-the-fact control that it gives me that even if the in-camera B&W is decent, I will still just shoot Raw and convert later.