Ehh; not yet trusting SSDs (or back in 2011 when I did my last computer builds), I prefer 15,000 RPM SAS enterprise drives. 50% greater rotational speed, SAS should be faster than SATA, and even Seagate (true) enterprise disks should be more reliable than WD consumer grade disks.

Now/next time I'll seriously consider SSDs.

Unless you could use an SSD? (most people who compile code are valuable enough that their time warrants the fastest thing available, no?)

Is "compiling code" an IO intensive (IO bound) task?

It certainly can be. Theoretically your OS should be pretty good about caching files in memory, but in practice I've measured significant differences when compiling large C++ projects on a fast SSD.