I can offer an update. I downloaded and installed the allegedly not (though probably) related Memento firmware from an allegedly russian hacker group. You can then use the Memor32 as a kind of mod chip. You can backup your games and play your backups, play homebrew run from the memory card or a flash drive, and it will also let you play import games on your US PS2. To play an import you have to make a backup of your game to an iso file (I use ImgBurn), patch the backup iso file with a patching program (it takes less than a second to do the patch), burn it to a disc and play the backup. I can vouch that it does in fact work for playing Japanese games, and works quite well. I haven't been able to test to see if it does anything about PAL games. I think you may have to patch such games to NTSC format with some other software, but I'm not sure as I don't have any PAL format games.
Currently the Memento firmware only supports DVD-format games, but they are promising support for CD format PS2 games as well as PS1 games in future updates. What it does so far it does very well and I'm very happy with it. It works and doesn't even require you to open your PS2, let alone solder anything. Just load the firmware via your computer and then plug the card into your PS2. FYI, the current firmware does have one problem - on my slim PS2, if I plug the Memor32 into slot 2 I just get a black screen at power up. It works perfectly from slot 1, though. They know of the problem and are working on it, though aren't sure yet if they can fix that. In any case I'm looking forward to the PS1 support, so I can play Japanese PS1 DDR games.
EDIT: the next update to the Memento firmware is suppose to support hard drives, including USB hard drives, but note that the USB ports on the PS2 and Slim PS2 are USB 1.1, so I imagine this won't be the answer for me with regard to reducing loading times. I plan to try it anyway, though - maybe the lower seek time of a hard drive will still mean an overall gain in performance. I'll find out.