I'm on it and everything seems to be going great. I was on Asacol and in remission when I switched. I did so mostly for the convenience of once-daily dosing. I imagine the time it takes to work is highly individualistic, just like it is for any oral med used to treat UC.
Status: Remission since May 2009!
Symptoms began in November 2008, ~4 weeks after giving birth to my son.
Diagnosed with pancolitis on 1/30/09
Currently taking Apriso (4 0.375g pills ONCE!! daily), mesalamine enema twice weekly, Natural Factors Ultimate probiotic 12/12 Formula, and Zoloft (25 mg).