I had this surgery back in July 2008.
"Was recovery painful"? The initial two days after the surgery is done is painful. For me it was extremely painful. However, there were other patients also who went for it but did not really find it all that painful. So, yes, I was the weird one driving the nurses and my doc mad because I was getting severe frontal headache and burning in the nose. I am a very sensitive person in every sense of the word. So I don't think anyone else will find it very painful.
"Did you notice an immediate improvement in your symptoms or was it worse before it got better"? It will take sometime for the nose to heal and feel the difference. You don't start to see any significant change immediately after the surgery. For me it took 3 months to feel the difference but for most people it takes much lesser. Yes, for me, it was worse before it got better.
"Was there anything particularly traumatic about it"? No, there was none.
"Is it really all that bad?" Sinusitis is a very common disease. Many people live with for whole life. Only in RARE cases complications can occur. The infection may spread to the linings of the brain and cause meningitis.
I don't think think there is any significant difference in the FESS procedure across various countries. The surgery is done under General Anesthesia (GA).
Finally, I would like to say surgery is the last thing that you should go for. When all other medications have failed to treat the disease or relieve the symptoms and the symptoms are SERIOUSLY HAMPERING your quality of life ONLY then should you decide to enter the operation theater. Also, don't think the surgery is going to change your life dramatically and everything will become perfect. It does not work like that. In my opinion, the purpose of the surgery is to relieve the symptoms but NOT to cure the disease. If you don't expect much from the surgery you may be amazed to see the improvements but if you expect too much, you may end up being disappointed as well.
Hope that helps.