The first hard drive (C) on the computer should be an SSD. These are super fast, and affordable when the sizes are small (250 gb or so). This will be your Operating System drive and where (most of) your program files get installed. My philosophy is that this drive is too small to hold everything, and too unreliable to hold your documents.
-mouser
If you're running a server, make sure your temp and logfile directories are all residing on another standard drive too. I'd suspect all that constant reading and writing is probably not too healthy for an SSD. And servers generate a lot of logging and scratchpad activity.
Just my

-40hz
Okay, first off I agree with you. I'm not a huge fan of SSD either. But... If the Temp file is on a more reliable - longevity wise - "Standard" (e.g. slower) drive, then it stands to reason that any process that is dependent on doing its workload in/out of the temp folder would then be restricted to/by the performance of the lower speed (presumably) mechanical drive. So wouldn't that negate the purpose of using a SSD? ...Or am I missing something?
I'm thinking that with the huge amounts of memory in machines these days are making the PageFile an almost moot point, so anything active in memory will most likely stay there. Then why not push the high traffic and ephemeral work areas off onto the higher speed (and arguably grenade prone) disk to keep the overall disk failure data loss exposure down? Sure you might - damn the luck on timing - lose the latest changes on the current project...but you're not going to lose all the projects in the folder next to it.
Lightning fast boot times
might - well yeah okay they are - be important for laptops and tablets. But for a desktop that has a much longer typical running cycle the extra 30 seconds is really that big a deal. The same thing could also be applied to application load times, laptop/tablet...gotts to be zippy ... Desktop...not so much.