Panasonic PT-AE4000 vs. Panasonic PT-AE8000
Overall, since the PT-AE8000 seems to be an evolved PT-AE4000, but with 3D and a whole lot more lumens. I haven't had a PT-AE4000 here in quite some time. That said, despite the increase in published contrast ratio, I don't see any significant improvement in black level performance.
Since the PT-AE4000's are by now, out of production (11/14/11), most likely they won't be around very long, from days to a couple of months.
While they are still available, some potential PT-AE8000 projector owners may do better for themselves with "last year's model." That would be mostly three types of home theater folks: Those with no interest at all in 3D, those looking for a big boost of lumens, and those desiring both the brightness and 3D abilities.
As those are the major enhancements, consider that in a typical year to year, one would expect improved performance for slightly less. If the extra 500+ lumens isn't important to you, nor is 3D, then it will be very hard to rationalize the PT-AE8000 for an extra $1000.
On the other hand, 3D and all those extra lumens do make the PT-AE8000 a whole lot more projector. With a price easily in line with any of the other new 3D capable projectors we've reviewed to date.