Although the Vaders have been a little crazy, particularly since ROTS, I'm one of the collectors that feels like the main characters should be out on the pegs periodically every year as well. I just wish Hasbro would use the best versions more frequently (VOTC Han, Evolutions Vader, EB/VOTC Chewie, etc.) I've often said that if they needed to have a Legends line I would just as soon they fill it with those "ultimate" versions of characters, so the ones on the pegs are at least the best they can offer for each figure.
I know I'm in the minority on this most likely, but I think I still get most excited when we hear of a new "ultimate, end-all be-all" version of a main character on the way (particular in the vintage line). After seeing what has been done in the vintage, evolutions, and now even basic line - there are some improvements that can still be made to many of the main characters (Bespin Han, Hoth Luke, Jedi Luke, TPM/AOTC Obi-Wan, etc. come to mind), and I like seeing those new versions released throughout the line. I really enjoy the background characters as well, and get excited for those too - but I honestly think if there were two "final" figures I had to choose between and could only buy one - SA, "ultimate" Bespin Han Solo or a background character like Wioslea, I'd pick Han every time. Not that I don't want Wioslea or other background characters, because I do, but I'd like to see the line continue to be a mix of new characters and "ultimate" versions of the big guns.