Today I have updated my Asus Eee Pad Transformer TF300T to Android 4.1 and was very disappointed. On Android 4.0 I used Ctrl+Space in Russian ASUS Keyboard to switch input language between English and Russian, and now it's not working! Just pop up notice that language was changed but language stays Russian. I've tried to use other languages, but all of them do the same. Restarting device does not help.
Ctrl + Shift does the job. A window appears where you can change the language. Worse than in Windows, but still...