In my experience with most Cisco products, the mantra is "latest version is not always best". It's sad, but true. Things that used to work just break randomly and you may be gaining new features with new versions, but in the same vein, lose a few features that used to work.
It all depends on what problems you're using ISE for - web auth, 802.1X, profiling etc.
Just to give you an idea - since July 2017 I have raised 19 TAC cases, and as a result created 7 new bug ID's - and all I am doing is sponsored guest portals. This is technology that has existed for years and it still doesn't work properly. I am not a fussy guy - I just expect things to work after seeing the flashy demos and powerpoint slides.
There seems to be a lack of quality control that allows these things to occur. The TAC are dealing with so many bugs instead of being there to assist customers with valu add functions.
I tried to upgrade from 2.2p2 to 2.3 and the URT tool failed (what a surprise). It seems that noone had tested the URT tool while PAN Failover was enabled. But the Oracle DB contained the setting and the URT just didn't like it.
In retrospect I think I have a guardian angel ... looks like 2.3 is probably only for the brave ...