I basically just collect the Christmas and certain other holiday sets now, along with interesting decor (love my bonsai on my desk) and Technic-like sets. Licensed sets are not for me for the most part (although the Voltron set is awesome).
Sold a couple I have spares of early on, but they can double in value over 2-3 years so I am trying to build up some inventory so I can support buying with selling eventually. Like the Christmas train set - I bought four of them for $100 each and now can easily get $300 gross for them. Especially because I got the old superior Power Functions with them.