DanceswithUnix has already made my point very eloquently. I'd just like to add that in my book *everyone* these days needs ECC memory. With the amounts of memory in our PCs the risk of soft memory errors from background radiation is quite high, especially considering the ever shrinking structure sizes chips are created at.
A "gaming machine" might not need it. I guess you'd probably rather yell at the monitor about poor programming when your game crashes or weird stuff happens. As soon as you do any real work, though, you really don't want to have skimped on the memory subsystem. BTW, doing a burn-in test on your new PC doesn't protect you from memory errors. At best it detects manufacturing issues.
I've been building my own PCs for the last 25 years. Only once, early on, did I *not* use ECC memory and was lucky enough to get a faulty memory module. Didn't notice it immediately and lost quite a bit of data, or rather, the data had been corrupted. Since then, support for ECC memory has been a primary requirement for me when building a new PC.