Yeah, good point. I was thinking that, too, but was willing to take the chance. But, as it turns out, it would've been a major hassle to get the wheel and the bearings to the mechanic on Friday--and I have the same situation here: rain in the forecast for tomorrow, so that puts the kibosh on my ride, anyway. The good news is that it gives me more time to solve this persnickety problem ... I'm looking at buying the bearings myself. A DIY youtube video on the G3 hub mentioned a Canadian website where he got his. (There were no videos for my particular model of PowerTap, unfortunately.) I'm looking for four 6901 RS bearings, according to the Saris owner's manual.

• Is there no difference in quality between ball bearings? Are they basically just a commodity?

If that's the case, then I'll just go with the most convenient vendor. On the other hand, Chain Reaction Cycles is selling four for only $12 (USD) plus $6 shipping, and they are 'Brand-X' brand, for whatever that's worth. I don't know how long it'll take to get them, but I'm willing to wait a few extra days if the quality is better.