Several people have had ignition switch problems. Mine is occasionally notchy. It helps to keep it well lubricated with graphite lubricant. Generally the problem manifests with an initial difficulty inserting the key, then being unable to turn the key once its in. Slightly turning and making sure the angle of insertion is straight can be beneficial if you are just having difficulty inserting the key.
Forrest did a nice write-up here. Pictures are nice, but not really necessary.
http://www.cbr1100xx.org/forums/index.php?...&hl=tumblerDo a search on "ignition" or "switch" in the garage and you'll probably find more references.
If you can have it replaced under warrantee I'd say go ahead.
I've seen some unusual behaviors when using the key in the gas and seat locks. It helps to press down on the cap or seat when you are turning the key to open either, and simply press down on the gas cap to close without using the key at all. The key is long and relatively soft metal, a combination making prone to disalignment and potential failure.