I bought a Park TM-1 the other day, I already think it's one of the most useful tools I've ever owned. Got it for $48 with the 20% coupon Nashbar was offering. I thought I knew how to tension wheels by feel, musical pitch, etc., and it is true that I could usually get it pretty close. But it sure is nice to be able to put an actual number on it, and "pretty close" is just that. For me, it makes sense. I'd bet most of the folks who've used them have the same reaction that I did, which was, "wow, that's cool."