aj78 wrote:It blocks the 8 pin header that several (possibly all?) Raspberry Pi DACs need, which rules it out for a lot of runeaudio type use.
"Pi Power comes with a 26 pin stacking header. With it, you can use Pi Power with any Raspberry Pi. B+ owners can use Pi Power as an adapter for 26 pin IDC cables that otherwise won't fit properly on the 40 pin GPIO header. If you are using a B+ and want the full 40 pins, you can add a 14 pin stacking header next to Pi Power." So not really an issue (for B+)
Using it with a I2S DAC will make the whole thing taller, which may or may not be a bad thing depending on the case you're using.
$15 is not bad, but you'll also need a wall-wart @ 9V/1.2A (ideally). Where I live, that's another +/- $40. And remember: if you can find a decent 5V PSU, it can be connected directly to e.g. the HifiBerry.
You may already have a suitable wall-wart and no space constraints. It all depends on your needs. Otherwise, 25mV ripple is not bad at all.