I've used G.I. Joe quite reliably for quite a few years and I've always been happy with their work. But recently we had some issues with our bathroom fans (which I installed and had G.I. Joe install the roof vents and ducting to the fans). I decided to replace the ducting myself and when I removed the ducting, I had found that the ducting that had been punctured which caused collected condensation to leak out and pour water down around the fans. The worst part was that they used screws to keep the flex ducting from coming off of the fans (normally a ring clamp and duct foil tape or tuck tape would do) and the screws were stopping fan's back flow flappers from opening. One screw was almost placed right on the hinge point of one of the fans flappers.
Lee is fantastic and I've used them for all of my furnace and fireplaces (installation and repair), but if you guys are reading this, PLEASE work on flex ducting installs and don't use screws anywhere near a duct flapper. :-(