I bought a used Habu Death Adder about a year ago, and didn't feel that it shot as well for me as a comparable Widow. I sold the Habu after a few months, and got all my money back out of it. One thing, people are curious enough about a Habu that they are fairly easy to re-sell. People like me want to try them out, but don't want to fork over all the money or wait all that time for a new one.
Just because I didn't like it as much as my Widows doesn't mean anything. As others have said, it's a very personal thing.