Maybe I missed it, but if how2 is still checking this thread how about telling us why you are looking to replace the tensioner? Is this because you have an actual problem with the one you have now, or is this just because you've been reading the reports from folks who had problems and are now gun shy? Just from the responses so far to your question, you can see pretty obviously that you can't just go by what a few people say. Some say the Hayden is basically crap, others say it's the best thing since sex (well, not really). The same goes for the stock unit, some think they are great and others think that one is junk.
So let us know what bike you're talking about (model and year), and why you think you need a different tensioner.
Jerry