To follow up on some of the questions and comments:

I'm not mentioning the brand because the bike shop is claiming that all brands have this problem. I wanted to see what the general opinion was rather than get into a discussion of this particular brand.

The warranty was for one year. However, this is a quality brand, so it's reasonable to expect many years of hassle-free use out of it.

The bike shop happened to have a replacement case (actually part of the case) on hand this time, so on that end things are OK. It's the lying and crap attitude I object to. Plus the bike is eventually going to need another tune up, so that chain case will have to be opened (and possibly broken) again. The chain case won't be easy to replace because it's Dutch, and perfectly colour-matched to the frame, etc.

Thinking about it over the weekend, I still don't buy this guff about the chain case being just so extremely fragile. There are all kinds of plastic bike parts out there that take a lot more wear & tear than this chain case (especially since it was an internal part of this chain case that broke, that only a mechanic would touch) and they hold up for YEARS. And this one just happened to break only the SECOND time it's ever been touched?

The kicker is, this bike shop is considered one of the best in the city. Their other mechanic who I've dealt with in the past is excellent (HE didn't break the case when he worked on it). This is a new mechanic, and I must say, when I talked to her, her attitude was pretty crap - that classic thing of talking down to me like I just don't know enough about bikes. Ugh.