While typing a string literal (i.e. anything between quote marks) intellisense is trying to help with code completion, but I feel that it shouldn't be doing this. Also, the options given in the list of code completion isn't filtering inside the string literal like it does outside.
For example, when I was writing the following assertion, as I typed encounteredException, I was given the option to autocomplete the variable. Good-o, that's what I expected.
System.assertNotEquals(null, encounteredException, 'An exception was expected, but was not encountered');
Then I started typing the message, and I got an autocomplete prompt with all the top level class names. As I typed, the list did not filter, even if I typed something I knew was in the list. But the fact the auto completion isn't working isn't the problem. I didn't expect the auto completion prompt to pop up in the first place.
Sorry about all the reports today as well. It's the first time I've really dug in and tried using TWS for work instead of just playing around to see what's going on here.