As a developer coming from a Windows background, I'd always find the different Powertoys and Sysinternals apps as invaluable tools in aiding programming. Is there something similar for a developer to watch for in the Mac world?
A lot of those types of tools are included with the Mac OS, and some are available separately from Apple.
There's no Mac equivalent of the registry - everything goes in the file system somewhere - and you can use fs_usage to watch that. In a terminal:
sudo fs_usage
Check out Instruments, part of the Apple developer tools distribution.
Not as such. Some of the Powertoys implement features that are built-in to the OS, some are available as various utility programs.
As for Sysinternals, there are quite a lot of them. If you want specifics I'd need a better idea of what you use, but you could probably duplicate 90% of the functionality just from a terminal window. Learning how to use bash and the normal Unix utilities would be a very good skill to have.
Mac OS X comes with a lot of unix tools like sar, top, etc. What metrics are you looking for specifically?