I'll second weedemon's comments.
I have an H20, but don't use it very often. I originally bought it for hash, but have come to prefer using a concentrate bowl.
With that said, the H20 works great once you get your heating technique down. I burned the living sh*t out of my lungs a couple of times by over heating the H20 while attached to a steam roller
The H20 can vape almost anything that will fit in a dram vial, and it attaches to all my favorite glass. In short, it's compact and versatile. On the down side, it can be tricky to use, and hard to clean. I can soak my H20 in 90% ISO for hours and the smell never comes out. The dram vials can be cleaned, but once you've burned something into a vial it will always have burn deposits on it.... however, vials are really inexpensive so that shouldn't be a big deal.