This is a minor point but annoying. I have just upgraded to version 10.0.2.0 and discovered that you must select a bracket before doing Alt+1, or Alt +7 to make a cell a heading or text cell. This was the case in version 9 but in version 10.0.0.0 it changed so you did not have to select the cell bracket you just did Alt+n. I dislike having to move my hands from the keyboard it was nice in version 10.0.0.0 while it lasted. Is this a bug? Could someone confirm? I don't see any reason why you have to select the cell bracket. Perhaps I am just being cantankerous... (In Help under Text Styling it just states Alt+n, no mention of selecting the bracket.)
This is not entirely true. You only have to select the cell-bracket if you have already typed something. When the cell contains no input then you can just switch the type.
If you indeed have already some cell-content, then the solution is easy: Press Ctrl+Shift+] to select the cell-bracket of the cell you are currently in.
Well spotted! I hadn't noticed the behaviour change in v10.0.0 -- probably because I've never found much use for the unshifted versions of the style shortcuts.
I've always preferred ALT-SHIFT-1 over ALT-1 because the shifted version works while I'm still in the middle of typing content into a cell, without having to move the selection point. The good news is that it still works in v10.0.2 (on my Windows 7 64-bit installation anyway).