It was pretty good: I'd give it a grade of B+. The worst problem was that there were only a few, huge files, but if you ignored that then it made a lot of sense. It was written in (then-)modern C++, clearly with a lot of care. It was clearly not written in a stream-of-consciousness manner. There were very few bugs that you could blame on lack of programming skill.
My personal suspicion in this area is that Satoshi was never (or not recently) a full-time programmer, but he was pretty familiar with computer science (maybe a student or academic?), and he'd read some comprehensive C++ book just before starting on Bitcoin, so he made full and correct usage of C++ features in a slightly messy way.
Is there any indication that he would be more familiar with another language, but chose to study and use C ++ because of its efficiency in memory usage compared to other languages? Since he believed that the easier it was to mine and maintain a node, the more widespread the network would be. And for that, the consumption of memory could not be high since many would hardly leave a computer exclusive to Bitcoin in the beginning.
Is it possible that he started the project using another language and started over again using C ++?