I bought a new Jupiter direct from Ten-Tec in October 2003 and have been very satisfied with its operation ever since.
It handles SWR better than a tube rig and has excellent sensitivity. CW operation is outstanding. SSB/AM phone is excellent provided you use a good mic like the TT706 desk microphone.
I got my Jupiter a few years after it was put on the market and there have been dozens of firmware updates to line out the bugs. I would suggest to any prospective buyer to get one and try it for 30 days. If you don't like it you can return it for a refund.
I would recommend purchasing the unit with the internal antenna tuner. Ten-Tec had a backorder of the add-on internal tuners for a while so if you buy it with the tuner already installed you won't have to wait.
I wrote a mini-review of my Jupiter - you can read it at http://n1su.us/tentec.html
73 Jason N1SU