I "bulletproofed" my 04.5 with a Goerend almost two years ago and I'm happy with my build. I've only put about 200 towing miles on the truck and maybe 6000 miles altogether since the build and it's a different truck with the Goerend vs my previously stock, and reliable transmission. I simply wanted "peace of mind" given that my towed load weighs almost two and a half times the weight of just the truck.
The biggest difference is when towing but truck shifts firmer and the more throttle, the firmer the shift whether towing or not. Throttle response is much better and is more akin to driving a manual from that perspective. I also seem to get a little better mileage and I suspect that's because the modded transmission is simply putting more power to the ground. The difference isn't much but it's there, approx 1 to 1-1/2 mpg better than with the stock transmission. Scott said all the stock components looked fine when they came out of the transmission and I wasn't experiencing any problems.
I had my transmission rebuilt by Patriot Transmissions in San Antonio, Tx. Scott, the owner is a great guy to work with and had no problem answering all of my questions and concerns. Goerend got out of the servicing/repair/rebuild business and focuses on manufacturing only now. Finding a shop that uses their products might be your biggest issue and I wound up taking my truck to Scott in San Antonio. I live in the Dallas-Ft Worth area.