I remember picking it up for free on release date, or whatever it was (yes, legally, Bethesda offered it)
Regarding the castle, I can't give a complete opinion, because I did not explore it much, but I believe it is a good home for a warrior lord or anything. I personally won't get it on my current character for RP reasons, but I remember really liking it. You get servants, a smith, guards... The quest isn't really anything interesting though.