I found that the benefits depend on your symptoms. It helped massively with the sinus headaches and pressure behind my eyes. It has significantly reduced the number of infections from one every six weeks to once every year or so. Any sinus headaches i get now can be managed with ibuprofen rather than me being tempted to take a drill to my head. The thing it hasn't helped with is the post nasal drip , which is still pretty constant and yucky.
the op itself was fine, try not to sneeze for a while after as that was painful!! Don't be suprised if it takes a few months for you to feel the full effects , and don't be suprised if you get a post op infection , given the nature of the area they are opertaing on.