The real question is can you get an ASIC miner today or in a few days? I prepaid mine back in November and still don't have it. If you can get one, do it - if you are just planning to order now - your already behind.

Over the next few months ASIC miners are going to be everywhere so the mining rates will be harder as everyone will have an ASIC miner. Just look at some of the pool rates over time - it's like when people realized you could use graphic cards rather than just a CPU.