Moving from Snow Leopard directly to Mountain Lion with Time Machine
In general you should not be concerned. However, if you are concerned I recommend you do the following instead:

Upgrade to Mountain Lion (do not do a clean wipe). Then re-install Mountain Lion again. Whereas the upgrade essentially checks and patches the system to make it the new OS, re-installing will effectively wipe the entire OS, leaving your user &amp; network data intact. This is exactly what wiping clean &amp; restoring from Time Machine backup via Migration Assistant will do.

If your system is acting wonky, it's just as likely that your user profile is the culprit. If so, both methods will keep your system potentially wonky. In this case you will want to  manually backup any necessary files (generally your home folder) to an external hard drive, wipe clean, upgrade, and then manually bring back the files you actually need.