Solid State Drives (SSDs) from Apple are too expensive. Thus, I purchased a fast Corsair Force GT 128 GB (plenty for a HTPC) at a fraction of the price to replace the "gimme" 500 GB 5400 RPM drive that Apple ships with the mini.
As smooth as can be!! iFixit's step-by-guide is spot on and easy to follow. No problems were encountered and I now have a screaming fast new Mac mini mid-2011!!
iFixit... no need to look elsewhere.