Mapolopus and Garmin GPS when showing too much detail on the screen,
Large audio books when FFwd or rewinding,
Whole newspapers on Repligo,
Hot Syncing large files,
and a few other things.

But they all seem to be caused when dealing with extra large files.
All of my applications still work for me, I've just learned to be gentle when using large files. I keep the GPS zoomed into "side street" level. I pause my audio book before rewinding, I read my newspaper front to back (instead of jumping between favorite sections, I transfer most large files directly to my SD card rather than Hot syncing them.

So my TX is still quite usable, just not the experience I expected from the latest and greatest Palm.

As for losing data, the crashes are really "soft resets" so the only stuff lost is something you just did. For example my audio bookmark might go back to the time before. Or my saved GPS destination might be lost. But I've never lost any real data like whole files or emails.

Maybe I'm a power user and expecting too much, I've got thousands of appointments in my calendar, I like to read Barron's (50MB) on my Palm, I put all of Germany, Texas and half of France on the GPS, I keep bunches of business cards scanned as tiffs on it... or maybe I'm not. But anyway my T3 behaved much better.

If you only need phone numbers, emails without giant attachments and some pictures of the kids, you'll probably be fine.

A guy I work with never complains about his, but he doesn't do much with it.

FWIW, another guy I work with has Tom Tom GPS on a HP PDA and he has to reboot his from time to time. So maybe all these PDAs have trouble.

Any way, I would not choose your next PDA by the Specs alone. Check out some PDA forums and see what people are complaining about as well