Your going to get two types of replies on RC springs. 1, like the two above. I'm included in that group that put a set of 4" springs on mine up front and don't mind the ride. It's stiff, but in my case, not a kidney killer off road. Plus you can't beat the price.
The other type of response you will get is that RC springs are Crap, ride rough and aren't worth a penny. You might notice that this group usually says to use Tuff country, BDS or Deaver springs. All three of which have a softer spring rate than the RC stuff so of course they ride softer and flex better too. You get what you pay for. Expect prices to be anyware from $200 or more for a complete kit with springs and shocks (rear blocks).
It comes down to personal preference and budget. If I had a couple hundred more in my pocket at the time I bought my lift I would have got Tuff country based on what I read here. Fact is, I didn't. I got my RC kit complete with shocks, hardware and a raised steering arm for $295 with Free Shipping. I would have spent more on the Tuff Country and still had to buy a raised arm almost doubling the price I paid for the RC stuff.
Bottom line I'm happy with my RC front springs. (shackle flip on the rear)