Ran across this ezine article while reading usenet news.
It's basically a comparison of the claims/literature/features of four a/c sealing products. Three of them appear to be moisture activated epoxies, while the fourth just swells rubber seals.
What I found intersting is some data from SSR, which manufactures cryochem, one of the epoxy based solutions. They warranty the repair, refunding the cost if it does not work as claimed. As such, they have visibility as to what/how/when the product is used. What I found amazing is that 1 in 6 applications of their product is to Mercedes Benz automobiles! Apparently that many evaporators get leaky, and that many owners get sticker shock at the replacement cost. I didn't realize our cars sucked so badly.
That said, I used cryochem on my 124 with leaky evaporator. It appears to have worked perfectly, so I'm quite satisfied.