There's plenty of reports floating around about the finicky nature of Storage Spaces in some setups...some of them are on versions prior to the final version, so hard to say if they were pre-release bugs.
If you like the idea of a full-feature OS but aren't sold on Storage Spaces to do storage pooling, then FlexRAID would be a good middle-ground. In the benchmarks I've seen, with parity calculations either in realtime or on a off-hours schedule, performance is pretty close to native disk speed... like in the 95MB/s and up territory. FlexRAID still lets you add to your drive pool later, the same way Storage Spaces does.
FlexRAID benchmarks are at the bottom of this article:
Cool. I'm down to unRAID and FlexRaid now. Given that speeds are similar with both. Now it's just a matter of preference if i go dedicated NAS or NAS/htpc route. Thing is, I don't have a budget to buy SSD for now so I might use my spare 500gb hdd to boot Win7 to run FlexRaid with the 2 Reds as data drives (1 is parity).