I measured the time to build navmesh for the above level, which I have been using earlier too. For build time and memory usage I measured the time that it takes to build a layer of navmesh from existing heighfield layer (rcHeightfieldLayer if you are familiar with the code). That is pretty much the bare bones of the process at runtime. I did not measure the time to rasterize temp obstacles yet.
I tested with a 32x32 tiles. The build time for a single tile layer varies from 0.01ms to 0.2ms, 95% of the tiles take less than 0.1ms. As expected there is some variation from run to run in the timings. The build process for one tile takes less than 15kB of memory. I'm really happy about that as all data could potentially fit in cache.
The data that needs to be stored in the memory takes 545kB for the above level, which compresses to 77kB using fastlz. What is interesting here is that the memory requirements for layers is smaller than for compressed compact heightfield even if there is a lot of waste in the layers. I think the win comes from the fact that there is no need for additional information about the layers.
Here's the complete test data in numbers.