I got mine this summer and have hunted about a dozen days so far this year with it. As was mentioned it doesn't have a variable zoom. I have the 65mm objective which is 30x power as well as the 85mm objective. The 95mm objective gives you 35x.
No problems at all with the eye piece. I've spent hours upon his behind it.
As far as tripods, I've used it with an outdoorsman's and their pan head. It works fine, but since I've been using it mostly standing I started using a manfrotto tripod and 701hdv head. My outdoorsman's will work, but the problem is that I have the medium with center extender. By the time I get it extended the top half is much longer than the bottom.
I'm certainly glad I purchased the btx.