I've finally upgraded! The old Acer C102Ti is out, and I've chosen a Fujitsu ST1032 as its replacement. This is an amazing piece of hardware. I've always loved the tablet pc profile, and struggled along with the Acer despite it's brutally sluggish performance (due largely to Acer's 256MB maximum RAM configuration).
A friend recently bought one of the newer Acers, which has significantly amped up horsepower but is also a big behemoth of a beast. Very un-portable, especially for a device which is intended to perform usefully in all those places where you'd use paper.
But the Fujitsu, now that's a different story. The ST5032 has everything a technophile could ask for. Thin, sleek lightweight profile. 12.1" display, clear and bright. 6 hours of battery life (and my test yesterday shows that's amazingly real). Plenty of application buttons, a wireless keyboard, bluetooth, Wireless a/b/g networking, and even a fingerprint biometric device.
Most importantly, 512 MB of ram, upgradable to 2 GB, and it's fast. All of my work with MindManager is blazing along, even with my largest maps (1000+ nodes).