The major change happend from FM10 to FM11, when it comes to lag in layout mode. FM12 is a little slower than FM11, but if you would have been using 11 you really wouldn't notice much.
So yes, that is normal behaviour.
I found out, that FileMaker 12 is extremely slow, specially in Layout-Modus by typing text in a dialog (e.g. formulary).
Specially if real-time Virus-Scann is activated. If I switch off Virus - Scanning FileMaker 12 is much quicker.
Maybe this has to do with automatic saving of changes in Layout-Mode.
Additionally I found out that FileMaker 12 behave much quicker if I switch off network connection - specially in Layout-Modus.
So I gues the problems of FileMaker 12 lay somewhere around "network access" and/or "disk writing / reading".
Maybe this is a hint for someone.