I call my wife Anna all the time. However there are many Annas in my phone book. It would be really good if it remembered my "favorite" choice for a given query. Probably just give weights to things that it finds, and sorts by that.
Yep, you are totally right. Making TA learn is high on my priority list - probably the next big feature I will release. One thing that could help in the meantime: if your contacts have last names, you can provide that to narrow down the search. Also, you can provide phone type. If you had "Anna A", "Anna B", and "Anna C", you could for example type something like "c a b m" to "call anna b mobile".