I'd look at:
Hard drive of some sort. Compact Flash card adapter for the IDE slot is a very easy and nice option.
Some accelerator card. A nice 030 won't be too too expensive. You'll want at the very least some fast RAM to get most out of her.
Networking or a compact flash adapter through the PCMCIA slot makes transferring files extremely easy.
It's worth upgrading the ROMs to 3.1 too, though it's not a huge deal.
Enjoy! The 1200 is an amazing machine.My candidate for one of the best computers ever made.