I have been playing with the 5000 now for about a month. I use mainly glossy paper, some lustre. I have a 4800, 9800, 4000 and now the 5000.
I don't have the technical expertise of Michael, and his criticisms are well based and right on. I'm probably going to keep the machine because I do like it and it allows me to locate the 4800 to another home that I work at part of the time, but there are some things I'm not real excited about.
Build quality ... materials used give this printer a little more "plastic" less commercial feel. Probably not a big deal, but its like some camera bodies vs. others.
Paper tray ... very large and cumbersome to use. It is a great big huge tray and it is a little bit of a pain to work with ...to put in letter size sheets you must remove the tray from the printer.
Smaller paper sizes ... I like printing a lot of 5x7 (7x10 paper size) cards on Moabs entrada paper, and I don't think there is any way to get this printer to do it at all. I haven't found one yet. My 4000 did it fine, I haven't tried my 4800 but I assume it will work since the 4000 did.
paper choices ... I do not like the feel of canon papers and to select a "paper" that is similar is really a pain. Talking to Canon they did confirm that the "specials" are basically 5 different levels of ink, and to create a profile they recommended printing a test pattern of pure black box with a pure yellow box in the middle, and determine how how far can go before you see bleed.
When I create profiles (have Eye-One UV system), I get a slightly "cooler" look in some tones on the canon ... not a real problem since you can only see this compared side by side, and the resulting prints are very good.
At this point I do not like the look of B&W but I haven't messed with it enough. To me it looks "cool" vs. Epson, but maybe it truely is more neutral. I know I'll have to find a way to warm them up more closely to the epson to get something I like.
My biggest concern is in areas that should have more "micro" detail. I do quite a bit of multi-shot panorama work, and also work with a p45 on a hasselblad, so I have some pretty nice detail in many areas. I am seeing some "blocking" in regions and loss of very fine detail. This may be because I've gone too far with my ink saturation so I am re-profiling moving from Special 4 down to Special 3 on Epson Prem. Glossy paper.
If you do a lot of matte and glossy printing this printer is a great option. If you don't, I'm not sure it really beats the Epson. However, the 16bit driver is very intriguing, and once I get more familiar with it I may change my mind.
So there you go ... a firm "undecided" fairly useless opinion.