So at _best_ you're looking at a minimum of 3 months before you can break even, and that's assuming the difficulty doesn't ramp up higher during that time, which is rediculous. I'm beginning to think that if $/BTC doesn't jump drastically or BFL/BFGA don't increase their hashing/watt/$ drastically, you could easily end up in a situation where you never actually break even.
A smart miner always buys hardware to support the network AND buys bitcoin to support the price.
Thus I recommend a 50/50 split of your mining equipment budget into hardware and bitcoins. You may be tempted to only do mining and sell all the bitcoins for a low margin profit (which is/was a way to ROI on the graphic cards), however this behavior becomes increasingly irrational once the ASICs arrive, since an ASIC is an investment which gets rather CONSUMED by the activity (graphics cards have ulterior usage patterns).