Tough question to answer. Mine is purring along now with nary a hiccup. Print quality very good, although I believe the change in black inks for the 5100 is related to some bronzing problems. A large number of the issues have been resolved, but some remain:
1) Print Longevity not nearly as good as HP, on par with Epson
2) Warranty for printheads is mediocre, and calculated cost of printheads by warranted lifetime is 24 cents per ml (vs. 3-5 cents per ml for HP heads). The Canon heads are $600 each (X2 = $1200 total), while the HP heads are $50 each (X6 = $300 total). If you are a lower volume printer, the warranty will expire before you get to the 10 trillion drops (approximately 2.5 liters).
3) Very poor software support, with known bugs/problems reported more than 6 months ago. They may eventually be corrected is all Canon will say.
4) Unknown whether the defective roll feed units are still being sold, so there could be significant hassle getting the problem fixed (though it will be eventually)
5) Very poor documentation
On the other hand, the HP is still very much in the teething phase, with firmware updates, reports of printheads failing, papers not available from HP or having quality control problems on the paper.
My guess is that the iPF5100 will probably clear up most of these problems, with the exception of the high cost of the printheads, especially compared to their warranted longevity.
None of the current alternatives (Epson, Canon, HP) sound really attractive to me--but all for different reasons.
--John
