So I just upgraded my Sanyo PLV-Z5 with the 8500UB and all I can say is wow. The Sanyo was a great projector when I got it (fall 2006) and the image improvement the 8500UB gave was nothing short of stunning.
I picked the Epson over the Panasonic because:
#1 - 2 year warranty. I just hate supporting panasonic with thier 1 year warranty, stand behind your product a little better! Normal people don't replace their PJ every year.
#2 - the color & image quality tendencies of the epson (at least per art's descriptions on projectorreviews.com) versus the panasonic are more to my taste. I like vibrant colors, deep blacks (a well light controlled theatre thankfully) and whites that aren't all crushed (look at a white jersey during a football game)
#3 - replacement lamps cost less, published specs suggest longer life. I put 4800 hours on the Sanyo over 4 years (well the household did - I wish I had that much time for entertainment!) so definately a "cost of ownership" factor on the epson.
Right out of the box I was impressed. 1080i content from the cable box, bluray and HTPC content, all in all a very good upgrade! I'll give it a couple hundred hours like this and then run through some calibration.
I watched some scenes from Apollo 13 on bluray, a show about Ducati Motorcycles on HD theater, part of a mariner's game (sigh @ being a seattle sports fan
), and a some other random bluray content (The dark knight, whiteout, season 3 venture brothers).