First of all, a lot depends on the year.
But in general I would say this....
Pros: Trailblazers are perhaps Chevy's best off road vehicle. It has just about all the standard specs you would expect to come with a medium-sized SUV. The SS version is a sportier version for those who want something a little flashier.
Cons: Although it has gotten noticeably better in recent years, in general, Chevrolet vehicles have not the greatest repair records. The only real exceptions to this are the latest redesign of the Malibu and Impala (though really just the Malibu) Like I said, though, the newer the better.
In short, if you're heart is set of the SS, by all means buy it. But if you aren't sure I might look at some other Mid-size SUV's. Personal recommendations would be the Honda Pilot, specifically the '03-'05 models. It has among the best body integrity and repair records of mid-size SUV's and for reasons that are beyond comprehension are cheaper than the likes of the Toyota Highlander, another great choice for Mid-size SUV's.