...
AFAIK, regtest mode isn't available on the 0.9 codebase, at least not easily... so having an easy testnet will most likely help dev work. I would suggest throttling your miner (on a low power VM) to keep the difficulty manageable.
Correction, regtest is there. Still, it probably would be helpful to have a low diff testnet.
Sure, I will mine very slowly by using cpulimit. I will try to produce about 1 block each 2,5 min at difficulty 304.