I have an SB65G2. Picked it up for £100 brand new.
Recently transfered what I could from my main system into this mainly because I don't game anymore and the power wasn't required. Also wanted to save some space in my small room.
Inside mine I've got:
P4 3GHz
2 x 512MB OCZ PC3500EB RAM
Maxtor MaxLine III 250GB SATA HD
Pioneer DVD-RW
Terratec DMX 6 Fire/LT PCI Soundcard
Nvidia 6200 Graphics Card
Did have a 6800GT in there but as I don't game anymore, I replaced it with a 6200.
My P4 was running at 3.7GHz in my previous ATX case system and there was no way I'd be able to run it at that in the Shuttle. Currently running at 3.26GHz for now and will try to go a bit higher at a later date. But I didn't get the Shuttle for uber overclocking. I got it due to its compact size and quietness (once you've done a few mods).
Its been absolutely rock solid stable and hasn't given me a single problem.