I owned a '96 Cherokee SE with the 4.0L HO engine and Command Trac part-time 4WD for 10 years. I average about 18mpg.
It's a practical car if you live in places where it snows half the year (I lived in Buffalo, NY, which is in the Snow Belt). Though if I lived in a more temperate area, I'd buy something more fuel-efficient.
I don't know about the Jeeps today (they are built differently), but the '96 XJ is one of the toughest cars I've ever owned-- Held up well given routine maintenance.