Using Bing Maps - Experiences?

I've been developing a mobile app ( Android initially ) that is almost complete and I've been using Bing maps with a Basic Key thoughout development, mainly because it gives the best look visually but now I'm realistically looking at the number of installs and that maximum transaction number for the free tier is looking a little on the low side. That said, apart from a massive spike a few months back ( I think I was hammering the placename lookup thing which I'm now not using at all ) I have precisely ZERO billable or non-billable transactions registered for what has been some extensive testing.

So...... I'm just looking for perhap some anecdotal reports from devs that have successfully deployed using OnlineMaps/Bing.

* Did you run into any issues or nasty surprises using the free tier once your app started getting some real use out in the wild?

* Did you find you had to go to the Enterprise subscription model either initially or subsequently?

* Did you find that it was much better to use one of the OpenMap solutions to save the worry?

I think you can see where I'm coming from, just looking to mitigate risk and stay on the right side of Microsoft.

Just to add, my app is free to download but contains IAP's so I think that places me outside of the Basic/Free tier anyway as this falls outside of the 'Not For Profit' model that is  stipulation of the Basic key usage.