Over a period of three years I submitted 470 tracks, 130 were forwarded (28%). Of those 130 I received 3 library contacts. So, I was averaging one contact for every 43 forwards. I've got 48 tracks spread across those three libraries now. And, I estimate that at least half, if not two-thirds of my returns are now in libraries. Listings get you writing, and that's never a bad thing!

Someone mentioned collaborations as a way to get into libraries, and I completely agree. Thanks to a couple of key collaborators I was able to get into well over ten other libraries. Collaborations are like any other human relationship,; they have their quirks and nuances. Some work out and others do not. There are some good threads here in the forums about collaborating.
Also, as someone else said, Taxi is not the only way to get your music into libraries. You can contact them directly. I've had success with this as well. When I hear music I like on a tv show, I watch the ending to find out where they got their music. It helps to record shows on your DVR so you can pause, because sometimes the credits go by way too fast. Then, find their web sites and look for any links having to do with submitting music. Libraries have their own processes, some will take unsolicited material (as long as you follow their directions), while others only take on new submissions during specific windows. Don't be afraid to reach out to them directly!
So, at the end of this lengthy response my main message is this: Do not despair! Keep going! Write Submit Forget Repeat!
Paulie