There are some discussions about Ukrainian hyphenation patters, a word file is even available on CTAN but according to some folks from CyrTeX-T2 mailing list, this file is basically wrong. This is yet to be done. Well, here is the background. TeX is very frequently used for scientific purposes which involve quite a bit of Latin letters. If one uses a pure X2, he needs to always switch to, say T1, if the necessity to write a Latin word arises.
Some people consider it very tedious.
So did I, once. If one combines Latin and Cyrillic letters in one table, the kerning in Cyrillic gets broken. This might significantly degrade the quality of some documents. There was a big discussion in the CyrTUG-T2 mailing list about this. Authors of X2 argued that one should always switch languages to provide correct kerning, and that users should not be allowed to freely mix different alphabets.