LMS 2.6 has a LOT of bugs fixed. I would highly recommend everyone upgrade. Thus far we have not seen any major issues with 2.6.
As for upgrading from 2.2, you will need to first upgrade to LMS 2.5.1, then move to 2.6. However, the easiest course is to do a fresh install, then migrate your 2.2 data once you are on 2.6.