I found out that Apple doesn't install the development tools or X11 by default, so I put those on. I had to edit a couple of preference files to work around bugs, and there's still one major piece missing that I can't do much about (but that only affects me and a small number of other folks).
Having lots of screen real estate is a nice thing. I went from 1024x768 to 1680x1050, so now I can put lots more stuff on the screen. I'm still getting used to that.
The machine is also a LOT faster. The only real measurement I can make is emulation speed under Hercules; peak speed went from 16.7 to 31.75 MIPS on one test I run. It definitely feels a lot snappier. I don't spend much time looking at the spinning beach ball of death. I've ordered 2 GB more memory (guaranteed compatible, lifetime warranty, $209 with overnight shipping), which will take the machine to 2.5 total. I'll have to really overload it to get it to swap.
Whee. Think I'll keep it.