I'm a very active cyclist and a new transplant to Charlotte. I'd say that it's about the same as many other areas, the city center is not a place you would want to ride. The outlying areas have great riding, you just need to be smart - don't ride during the commuting hours!
There are great organized rides leaving from many of the bike shops and Y's. Check out these sites:
BikeCharlotte.com - Your Local Biking Resource
Tarheel Cyclists
Local Events - bicyclesport.com (http://bicyclesport.com/page.cfm?pageID=37 - broken link)
Rock Hill Bicycle Club
See you on the road.
And everyone else ... Share the Road with cyclists