Well I'll chime in since this is an interesting subject.
I think the Pearl looks the way it does because RIM designed it to look attractive to the 190 million "Non-BB" cell phone users that RIM is going after. Hence the chrome, black, shine here and there, etc.
Those 190 million non-professional users don't buy phones based on how sturdy the case is, they buy on looks. Imagine the Pearl with 7100t looks and construction.
If the Pearl looked like my old 7100t, probably 99% of prospective customers would not give the phone a second look. I used the 7100t for about 18 months. I heard nary a compliment that phone. Let's face it, the thing looked like a government-issued device.
As to construction quality, I do wonder what happened there. The Pearl took three years to develop. That is a long time. Was all the effort put into the innards without regard to the case? I dunno.
Some of the pieces seem easy enough to beef up without adding weight or bulk to the phone, such as the battery cover locking mechanism. I suspect RIM will upgrade that area or new models will address the issue.
I don't have a problem with the phone's fit and finish because I have a total BSE skin and I keep it encased in a Seidio rubberized case. The phone feels pretty solid and the surfaces are protected [and out of view since the case covers most of the phone except the keyboard and display].