That's also my experience. The price tag makes it neat to tinker with for a day or two but very few people seem find a real-world application for it.

I tried to use mine as a cheap Zoneminder surveillance solution, but the rPI barely managed a single camera at 640x480 with 2 (two) fps and motion detection. It was overclocked to "Turbo" too.

Maybe you should consider upgrading your mac Mini to a later ~2010 model then!

Performance is no issue on these machines because Plex' GPU hardware decoding implementation of the 320m is really, really good.

You can play back a full bitrate 1080p Bluray rip with < 10% CPU usage and get plenty of headroom for other stuff in the background (multiple other PMS transcoding sessions, unpacking, etc). Add a small SSD and that HTPC/Homeserver-machine should last until 4k gains traction.

The rPi is just too slow for high quality playback. OpenELEC comes pretty close and out-of-the-box HDMI-CEC is amazing, but the bad performance ultimately ruins the whole user experience for me.