Well if Meg‘s going to complain about spelling, and I fully support her in this endeavour, then I’m going to vent some grammar-related fury. A prize is on offer to the first person who can find a legitimate spelling or grammatical error in this post.
When did ‘to used to’ become an infinitive verb? Granted the usage (that is the correct usage) of the construct “subject used to infinitive” is more complex than the similar (in meaning) “subject verbed”, but it’s not so complex as to be incomprehensible. To give an analogy for those who don’t see the error in “I didn’t used to”, consider the phrase “I didn’t must”. Would anyone try to form a sentence around such an obviously erroneous fragment? Neither ‘must’ nor ‘used to’ should be used in this manner. So what’s the alternative? You used not to know but now you do.