Well, after fighting with it for a while, I ultimately gave up on writing code with Ultimate++. The learning curve is too steep and the support is bad enough to not be worth the time. Don't get me wrong, it's probably a good toolkit overall, but it parts of it which seem like basic system services are nonexistent or require work to get right. If it had a bunch of people behind it working on patching the missing bits and/or had more complete documentation, it could be really nice. When I was contemplating ditching the toolkit, I gave wxWidgets another go, and, to my surprise, it installed and worked right out of the gate. I'm not sure what gave me such a hard time getting things to build last time around. *shrug*
Anyway, I started work on what I consider my first app when learning a new toolkit: a program to randomly generate bingo cards from a word list. It's a helper app for some teachers that I work with, and it's a good first project because it familiarizes me with basic UI programming, file I/O, and printing. After a few hours, I've got everything working except the actual printing implementation, which should come soon enough. As soon as I have something worth downloading, I'll probably post it on my website. Not BeOS, but if the port of wxWidgets to Haiku takes off in a reasonable amount of time, it will be also for BeOS.