The first week is the worst if its open surgery. But within a month you'll be feeling okay.

I had open no mesh surgery in April 2011. Was able to complete a 10k obstacle course race 6 weeks later. I took it easy at that race, but mentally it was really important for me to show myself that I wasn't totally incapacitated. Did an olympic triathlon 2.5 months later without any problem. But it took another month or so before I could even consider sit-ups.

Cosmetically, I still have a scar and my lower abdomen isn't flat despite a regular regime of about 400 sit-ups per day. Its just how the abdomen healed. :-(

Pain is largely gone, but occasionally it'll hurt for a few minutes or days. Always goes away.