I have several of them.  I bought them for the "expanded info and pictures"/dictionary aspect to them as opposed to any desire to play the game.  I bought all of mine in the early-mid nineties when I wanted every aspect of the Star Wars Galaxy to be explored.

I was also trying to make a LucasArts style adventure game off of Heir to the Empire, and I think the HTTE Sourcebook was the first I bought.  I still enjoy pulling them off the shelf and flipping through them, and I have enjoyed looking at some of the newest ones at the bookstore, but I haven't bought any in a long time.

I was always tempted to buy them, had a friend who had a couple sourcebooks for reading. Tried playing it once in college. Ugh. So many D6's, and my friends wanted to be Jedi and were rolling something like 20d6, which is crazy.

I don't remember much about it other than the dice. I remember wanting to be a non-combatant because people not involved in the Civil War interest me. A gambler, I think, who was only going to obey whatever the flip of the coin decided (much like Two-Face). However, a stray turbolaser blast blew open the deck of the ship I was in and killed me within five minutes of us actually starting to play after hours of character creation. I think we retconned it out, but I don't remember actually playing after that point, only observing.

I never played the WotC, but I imagine with my D&D 3e and 4e experience it would be a little easier.