Homebrew PCBs

The R320 is limited to 1440 DPI (well, 5760x1440 but square pixels are 
nice) but that's probably still more resolution than needed for what we 
can home-brew.  The R280 can do 5760x2880.  Anyway, if your existing 
print software can be told to print at 1440 dpi, and your EDA software 
can produce a print of that resolution, you should be all set.  The 
interesting factor will be if the print software can be told to put down 
more ink than normal (choose ultra glossy film if you have a choice). 
My software uses the smallest drop size but 100% coverage (no dithering 
or halftones).

An unrelated thing you might think about is how you're holding the film 
against the PCB.  I only get good results if I (1) print the film in 
reverse, so that the inked side is against the PCB, and (2) use a vacuum 
to hold the film tight against the pcb (gravity won't work).

With a decent film (jetstar, silkjet, etc), high enough resolution, and 
enough ink, you should be getting jet black prints with crisp edges. 
With something to hold the inked side tight against the PCB, you should 
be getting crisp edges on your etch resist too.