In reply to TobyA:
I have had a pair of defrosters for a couple of years, they leak like a sieve... But do keep your feet warm for the most part, but you might get trenchfoot.
Don't worry about BOA, they have a separate warranty all of their own and will send you out replacement parts for free.
I've not tried any other brands so I can't comment, though I hear good things about Northwave and Lake.
Unfortunately, they all have the massive weak point of a giant hole that is needed to put your foot in the boot. Some swear by cutting the cuff off a pair of marigolds and slip it on before the boot to recentp water running down your leg into the boot. I've never tried it, too much faff for me.
cheers