Unless the glide is sealed properly to the wand it will probably leak air, especially at the ends, so could well leave the carpet wetter. Get it fixed on with a good dollop of silicone sealant and it works fine.
Funny how experiences differ, I find a glide picks up crap from the edges better than without one!
I wouldn't say you need to "boil" your glide, but certainly dunk it in hot water for 5 minutes.
Also be prepared to use a stanley knife/blade/chisel to shave your glide so it fits your wand perfectly. I have a westpak, for which i had to cut out a slot in the glide to go round the bracing piece that keeps the wand lips apart. I also had to shave it a bit to make room for the screw head on the other side.
Line the inside of the glide with silicone, and put some on the wand too. But only put the silicone on when you're sure the glide fits otherwise you'll get in a right mess!