I've only eaten here once, but I didn't have a problem getting a ressie. DH really wanted to eat here & it was his birthday. I called about 2 months before our trip to make the ressie; got the day and time we wanted with no problem. Granted, it was lunch and on a Friday, so maybe that made the difference. I live only about 2 hours from WDW and go often, so I don't generally make ressies for anything - only if it's a special thing. (DH's 42nd birthday qualified.)
We both enjoyed our meals, but I can say that it wasn't the best meal I've ever had on property. (That honor is tied between Flying Fish & Citrico's.) The atmosphere was nice, the food was good, and the service was great. If you've never tried Le Cellier, try to get to get a ressie & go- I think lunch may be a little easier to get into. Above all, go in with realistic expectations. There are lots of great places to eat in WDW.