Upload & Sell: On
Jane - I've been making my own custom profiles for something like fourteen years now - first for the Chromira and Lightjet prints I had made at labs here in Los Angeles, and later for the series of inkjet prints I've owned myself. Without a doubt a good custom profile makes a huge difference in print quality and reduce the number of prints it takes to get to the final print to a point where the first print is usually the last.
There are a couple of issues I have with your write-up. One is that there is no mention that with the current versions of Photoshop, there is no way to properly print a profile target as you can't turn off color management. There is a utility call the Adobe Color Printer Utility, which is a one trick pony that does properly pass the files unadulterated to the printer, but it also apparently does not run in the latest operating systems.
The second is the vague referral to the Epson printing mode known as Advanced Black and White. My experience with Epson ABW printing is exactly the opposite as yours. It's been extremely predictable and stable and is again one where the first print is almost always the final one. ABW is not color managed, but does expect to be getting a gamma 2.2 tonal curve, so sending Adobe RGB even when it's a black and white image, is the easiest. Unfortunately, the interface has been bunged up in CS6 vs CS5 and it's more confusing, so printing ABW out of CS5 is preferred.
Epson, in particular, has been very good about supplying very good profiles for their own printers printing Epson branded media. Even so, I still see minor improvements making my own, and of course, always do for third party papers.