http://www.rtings.com/tv/learn/size-to-distance-relationship
Unless you plan on sitting closer than 8 ft in front of your TV (which is pretty close for 60", IMO), then you're not going to notice much of a difference.
Also, the lack of content renders 4K effectively worthless (for now). I think it will be quite awhile before we see 4K as ubiquitous as HD is today. Heck, most HD isn't even 1080p yet (besides Blu-Ray, of course).
All that said, 4K TVs will be awesome for that theater-like experience in a dedicated media-room when they finally start releasing content in 4K. I just don't think I'd ever use a 4K for my "every-day" TV.