No, Not Yet!
MobileMe will remain available until June 2012. All 3rd party applications that support MobileMe Syncing must be updated to support any equivalent iCloud functionality. If you use MobileMe Sync with Spell Catcher X or any other 3rd party software, you should not move to iCloud until these products are updated to support iCloud.
We are currently investigating what will be involved to implement iCloud syncing functionality in Spell Catcher X. At this time, while we plan on adding iCloud support if it appears to be possible, there's no way we can predict when it will be available. Stay tuned.
You may well be asked to setup your iCloud account after updating to a version of Mac OS X that includes iCloud support. Best to stop and think about it first!
If you do migrate your MobileMe account to iCloud, realize it's a one-way trip. You will not be able to use MobileMe Sync with Spell Catcher X or any other 3rd party apps you Sync with. There's no going back.