Personally, I love the Synology devices from a features perspective. I do wish they had a little more horsepower (in terms of memory/cpu though).
If you roll your own, some of it may depend on where you are planning on having the NAS. If you are putting this near your entertainment center, I would look at a quieter power supply and some quiet fans. A nice fanless and some Noctura case/CPU fans keep the noise level down. If this is sitting in an office where noise isn't a concern, then it doesn't matter as much.
Ep, glad to see you come back and tidy up...did want to ask a one day favor, I want to enhance my resume , was hoping you could make me administrator for a day, if so, take me right off since I won't be here to do anything, and don't know the slightest about the board, but it would be nice putting "served administrator osnn", if can do, THANKS