The ability to crash and to frustrate administrators.
Out of the box, not very much, but you could get Scripsit, filepro, Informix and Unify. Quant made a statistics package. VI, MICNET, UUCP and CC were add ons (part of the development system). Sound Ideas had a BBS that ran under Tandy Xenix. Tandy also had the VIS system that would set up a hypertext (but not html) dial in system. There was no ethernet support.
Unmodified, but with hardware upgrades, it supported up to 1meg RAM, 8 external serial terminal, and one parallel printer. With an external hd system, it could address up to 280 meg of MFM hard drive space and 20 meg of bernoulli drives.