The church, as of August 2013, is fully restored and the scaffolding is down. The inside is covered with 13th century frescoes, including a cycle of the life of St. Nicholas (later morphed into Santa Claus) as well as portraits of the ruling tsars and tsarinas of the times.
Very well informed guides took groups of five to ten people at a time into the climate controlled church. The interior is small, basically a narrow apse and the nave, with an outer area that has an exhibit about the restoration work.
The frescoes were some of the most beautiful and best preserved (and restored) I saw in Bulgaria. They approach in beauty and artistic sophistication those found in Italy of that period. Rebecca West wondered,(though she was talking about Yugoslavia but still relevant)how far could this painting have advanced but for the Turkish occupation. Compare these to the Russian Revival style paintings from the 18th century in Alexander Nevski and post-Ottoman churches (inferior, almost cartoonish in my non-expert opinion) to get an idea of the various forces that have shaped this part of the world. Boyana restored is certainly worth a visit.
While you wait your turn to enter (the day I was there I only had to wait five minutes or so for the group before me to come out) you should walk around the grounds. The guide, who was also waiting for her turn to enter, spoke about the history of the church, answered questions about the exterior and talked about some of the graves (and their inhabitants)in the nearby cemetery. There are food stands and cafes in the car park just outside the church.
It was about a fifteen minute and $10 or so cab ride from the west (Ovcha Kupel) bus station in Sofia but there are several delightful trolley cars you can take from downtown Sofia to the last stop, Hladinika, then a two minutes walk through a park past some food stands to Bus 64 (it's the beginning of the route)to the Boyana Church stop, about 20 minutes. It costs about one dollar. (I took the bus and trolley back.)