A couple of months back I asked mmpool why he doesn't upgrade to 0.9.x. At least he's running 0.8.x, so he's doing better than most. His answers are above.
Here's my take. The big miners are stuck because they don't want to fork the block chain like F2Pool did. What we really need is a client which is guarenteed not to fork the block chain. Has mmpool tested 0.8.x enough to guarentee this? I don't know. Obviously the majority of miners don't think so.
I think the best option is to write the code so the new mining rules won't kick in until 95% of the blocks are being mined with the new client. We would have to set the rules to match the old 0.3.24.3 client, then once we have 95% of the miners upgraded then, and only then, would the latest set of rules kick in. This is a tried and tested method.
We would need to test and advertise this very well so miners would know that it's safe to upgrade. We could do this with the next major Bitcoin client as the baseline, which should be 0.12.0.
If you guys get the code done and tested I'll "advertise" it to the miners in a hurry. Wish we could this quickly, like 30-60 days. Gotta feeling things are gonna take off by April.