On my 03 Trailblazer the fit and finish is suprisingly good considering it's a Chevy. No rattles or squeaks, but only 700 miles
The seats aren't as comfy as the Envoy, and have a plasticly look to them (LTZ has leather standard). The dash is much improved over my pop's Tahoe. Much better material, some sorta pushy stuff and not that rock hard plastic.
Over time I dunno. I've read in several different places that squeaks and rattles are minimum over time, suprising considering the make. The triplets (Envoy, Trailblazer, Bravada) are all basically the same mechanically. The nod goes to the Envoy for more refinement. Wood stuff on the dash, air suspension, etc. I grabbed one because of all the discounts I got ($36,500 MSRP, paid $25,300) and love the way it rides.
The engine isn't broken in yet, but I'm getting about 22 highway and 17 city right now. Most folks at Edmund's score about 19-20mpg average.