The EE are a mixed blessing. Some scenes really add a lot to the films, while others you get the impression that there was a reason why they were left out in the first place. You have to remember these are not for the average viewer--the theatrical cuts remain the definitive versions of the films and Jacksons own preferred directors cuts--the extended editions are for those who want more, who are willing to delve into a longer and richer world. Overall, the full extra-long versions are very engrossing, although to do TTT and ROTK in one sittting can test the limits of one's patience, running nearly four hours each--the longer and more uneven pacing doesn't help when you are at the 3 1/2 hour mark.
Some have recommended splitting it into a mini-series--each film has an intermission, and the edit is constructed the way an intermission should, with a key dramatic point and the seminal story change occuring at the point of break. Thus, each half is satisfactory and has its own arc. Watching the films as six 90-120 minute segments rather than three 220-280 minute segments may be preferrable to some.

The EE-only big box sets are also great for their plentiful extras, pretty much the most extensive series of special editions ever made.