This meant more work, of course, and could only be done with Multiterm termbases and AutoText entries, and not with suggestions coming from AutoSuggest dictionaries (which are automatically created by Studio from TMs and not user-editable).
With the release of Studio 2011 SP2 a few days ago, this is no longer an issue. There is now an option to enable/disable the case-sensitive feature of AutoSuggest. Here's how to do it.
Note: If you haven't downloaded SP2 yet, make sure you do, as this feature is not found in previous releases.
Go to Tools - Options - AutoSuggest, you will see this screen:
The checkbox is checked by default, so if you liked the original AutoSuggest behavior, just leave it checked.
Uncheck the Case sensitive checkbox if you want AutoSuggest to override the case of your entries. With "Case sensitive" unchecked, suggestions are adapted to the first letter you type, whether uppercase or lowercase, as shown here:
I think other Studio users will agree that this is certainly one of those little things that make a big difference.