Hi Stringrazor.
Well done for holding out so long. AJBR's are still great players with Rockbox, and sound quality, stability and battery performance has yet to be comparable on new ports (AFAIAA). I would guess this is heavily connected to the fact that no-other port has had an official release yet.
Basic functionality with an iPod should be mostly the same, with the exception of losing recording but gaining larger, higher def colour screen in a MUCH smaller unit. Battery life won't be as good for a while. As far as I am concerned, sound quality is pretty damn good on the iPod, but I never fiddle with EQ and my eardrums have been heavily abused over the years. There's still a lot of optimisation to happen, but it's getting there.
When you say "lasy years model" iPod... what do you mean? Photo, Video or greyscale?