Tim,
Because I print so much, it is very second nature for me to prep images and sometimes just dump them into a folder for printing whenever I have a batch of things I need to get out. That does make it a lot easier. I also print with the ImagePrint RIP on my 7800, and although it lacks the automatic paper feed that I still have on my Epson 4000, I can lay things out easily, and cut them up later. I have gotten a routine down that makes it very easy to go from image to print very quickly, and because the printers stay on so much, I never have issues with clogged heads, etc. Also, the RIP really makes trying out new papers and things very easy, so I create fewer excuses for myself ;-)
All that aside, your comment about making it easy to do the 4x6s is serious for some of the manufacturers. Canon still has that "stupid" Print button even on their 1-series cameras. I have yet to ever use it. However, folks shooting JPEGs on other cameras can quickly plug into some of the smaller printers and just let them run through whatever images you have marked. The Canon Pixma printers do this as do some of the HPs, to the point that you simply drop the camera onto a dock on the printer, and it spits things out for you. That is very simple and pretty fast. Limitations exist, such as print size is 4x6, with a few going to 5x7. Very minimal adjustments to anything, except some cropping and straightening, which is about all that is required.
I almost bought one of these smaller printers just to crank out small prints quickly, but immediately ran into my own "wall" in that I only shoot RAW, so I still need to do the conversions and stuff. I could shoot both RAW+JPEG for this, but I just never do, so that extra step of having to convert things automatically raises all those "critical" adjustment arguments, and that alone keeps a lot of prints from ever being made. There is a point when one has to just let things go and not worry that each is a masterpiece print. At 4x6 size, nobody really cares or notices any of that, as you noted.
Oddly enough, I have a cheap Epson R380 printer that I use for doing CD/DVD printing and paperwork stuff. I also have several boxes of Epson Premium Glossy paper in 4x6 size sitting next to the printer. I find myself tossing in a few sheets and sending stuff to it just for fun. The colors do not match my 7800, but they look acceptable for 4x6s and make the process entirely painlessly easy to do. (I never provide 4x6s to clients, and if they do ask, and I am also doing other sizes, everything gets retouched and printed on the 7800 for consistency and colors. That is my practice by choice. There are a couple of clients that do want every image in 4x6s for scrap-booking, and there I find it much easier to just upload to Wal-Mart or Costco and get cheap prints done on their printers to pick up later that day or have them sent to me for not much extra. That is actually much, much cheaper than doing my own.)
Lots of options out there, but I still think the biggest hurdle for us photographers is dealing with what is really acceptable quality for the average viewer, but nothing close to what we want to show folks of our work. The hardest thing is for a serious photographer to just do snapshots for fun. Once you get past that, it really is O.K. for things not to be perfect every time you press "print" ;-) (For stuff going out the door to clients, etc., I do make the best efforts, as my name gets associated with those prints. For fun stuff, I really do not worry as much, and have found that even my worst snaps are still better than what most folks shoot, so it still looks fine. We are our own harshest critics. That is good, but can also be limiting for some things.)
LJ