Surprisingly powerful. I used it to drill 3 inch deck screws into 2 inch cedar for 2 hours straight. While the unit will heat up over time, it cools down quickly. But more importantly, it is powerful enough to do that job well without any issues at all. I am totally satisfied with it. It is also more compact and lighter than the 18V Black & Decker I owned before. Yet outperforms that old 18V by a wide margin.
Update: It has now been a year and this drill still performs like it did right out of the box. The battery keeps a charge for a long time too.