I heard tons of recommendations for the Armalite riser with integrated rings, but I wanted to use a red dot scope, a lower power hunting scope, and a higher power target scope all on the same flat top AR. I wasn't about to buy two of the 1" versions of the Armalite mount (for the conventional scopes) and 1 of the 30mm version (for the red dot). I bought the RRA flat top riser base and am using quick release rings for each scope.
I tried medium rings for the scope on my flat top and it wasn't high enough to look through or even high enough for the objective bell of the scope to clear the free float tube over the barrel. Standard high rings were just barely tall enough for the scope to clear, but still was too low to get a decent image through the scope without crushing my cheek into the stock.
Look on this page to see a picture of the RRA flat top riser base. I like the looks of those Bushmaster mini-risers, too, but since I had different ring spacing on each of the three scopes, I went with the full rail instead.
http://www.rockriverarms.com/scope_mounts_slings_&_bipod.htm
I use Leapers rings with it. I was pretty skeptical of using such cheap rings, but they are working great for me and return to within 1.2MOA of zero (~1.2in @ 100yds) or less on two tries of each set of rings. Testing the 30mm rings used with the red dot scope might have just been luck, since it's pretty dang hard to put that 4MOA dot exactly in the center of the target compared to the 36X target scope. :)