Here is some ebook sales insight for the interested. On the iBookstore, sales has been pretty spotty. The most I have seen is half a dozen a month. On the Google Play Store, stats are very similar (and still not easy to keep tabs on).
On the Kindle Store, things are far more interesting. Sales has picked up fairly well and there is now a good cadence to it. Here is the Kindle sales chart for the past 60 days and you can see the sales trend there. The Kindle sales nicely complement the physical book sales which is consistent and a good 4-5x higher than ebook sales.