My advice, based on three Trailblazers and Envoys in our family is yes, definitely buy one. My brother-in-law has two Trailblazers. One was passed on to his teenaged son at 165,000 miles. It now has close to 200,000 with very few problems. It is a 2002. His 2005 has 110,000 miles with never a single problem. Our 2003 GMC Envoy (exact same vehicle) has 90,000 miles with absolutely no problems at all. Ours hasn't even required brake pads yet.
These are incredibly good riding, powerful (even with the 6) and very well built vehicles. Two of our friends have bought used Envoys based on our excellent experience and they are very happy with them. One was bought with only 20,000 miles on it and one had 110,000 miles. Both are like new.
I hear a lot about fan clutch issues with these cars, but no one I know has ever had this problem and it is a very easy and cheap fix if you do encounter it.
And my advice is exactly the opposite! We've had three in our family as well. Two of them had the front ends fail at 30K miles or so, and the third one made it to about 60K miles. We also had many many repairs with our last one, and it was in the shop every other week! I traded it in, and it still needed almost $2K in repairs, so we put that money into a much better designed import SUV.
As far as the fan clutch. That is not always the problem when you hear the "jet engine" sound. Ours was an air pump on the transmission, and had nothing to do with the fan clutch. It all depends on where the sound is coming from. We also had the notorious stalling issues with ours. We had the injectors cleaned, and it helped a little, but not for long. It idled so poorly, I could barely back up to a trailer with it, for it would surge and then die off, and surge again. It was such a pain to drive.
I would not recommend anyone buy one of these trucks, especially used. They are under-designed, and very poor quality, based on my personal experience.