I'd recommend a more up to date iteration of LPV, which includes corrections and annotations for the original paper, plus a DX10.1 demo with source
If you want a fast and proven technique for real-time diffuse indirect lighting you should look into light propagation volumes as proposed by Kaplanyan and Dachsbacher
I wouldn't call it easy to implement, but it's still a lot easier than the cone tracing technique
Thanks for the link, wasn't too sure of the latest paper on the subject as I get my information about the technique from GPU Pro 2
GI isn't as this important in games? Well, maybe because it was a forest. A scene in a building would need GI to be realistic, I think?
Even if you don't directly see any drastic changes to the scene, GI will still be a very important factor when it comes to realistic lighting in pretty much every setting.
LPV doesn't support occlusion, that's its con.
I think you're confusing the LPV technique with VPLs. Indirect occlusion can be perfectly incorporated in the LPV technique by using a geometry volume.