I just picked up one of these on the cheap ($12AUD to be exact) as a kick-around box for LAN's - I upgraded the power supply by getting a SFX PSU, and mouting it via cutting a aluminium plate to size of the OEM PSU with mounting points, followed by a cut out inside that for the SFX PSU and it's mounting points.
The next problem after that is size and mounting - The PCI-Ex16 slot isn't positioned for dual bracket GPU's (like the low profile GTX750 Ti), the riser doesn't aliviate this as it positions the raised PCI-Ex16 slot below the raised PCI slot.
So you come back to the problem not being able to utilised dual bracket GPU, there are ones that use a single bracket but still have a dual bracket-sized cooler, so you run into the problem of the cooler either touching the board, or sucking in hot air straight off the motherboard.
You also need to keep in mind the GPU doesn't extend much further than the PCI-Ex16 slot, otherwise it'll touch the CPU heat sink.