If you are into 5 channel stereo or something like that, bookshelves would be fine. I think for actual surround content in movies and the like, RS wide dispersion works great. I have used both in my HT setup, and I prefer the RS. If you have a single bookshelf right there pointed at your listening position, I think you gain a bit of clarity from surround content but it is very localized and you always know exactly where the sound is coming from. RS by design really open up the surround content by not aiming it right at your head but bouncing it off the walls around and behind you. It makes for a more enveloping experience. You could try both though and see what you prefer, it is not like bookshelves will sound bad or anything. I wouldn't say it is a major upgrade going with RS, just a tad more open and subtle.
