When I took a cursory glance I didn't look at the core system or kernel - I was doing a once over of the entire code base to check general coding style and what stuck with me was the amount of C++ code
???
The ReactOS source code (v.0.3.0, "reactos" directory) consist of: C: 92.22% C++: 4.69% ASM: 1.01%
The ReactOS Kernel (v. 0.3.0) consist of: C: 95.70% ASM: 4.30%
The whole ReactOS trunk directory (sept. 2006; with subsys and rosapps): C: 78.70% C++: 5.46% ASM: 1.41%
All percents based on the SLOC stats, which has been gathered by using David A. Wheeler's 'SLOCCount': http://www.reactos.org/history/10y/statistics.html