In theory I don't like it. In practice, I have done it this year (Abreu, Burrell, Lieberthal and Helton, Walker, Payton). And I've never really felt like it didn't work. But as someone mentioned, a rainout or two could really hurt, or perhaps bad matchups could impact you more than normal.
I'm still working on swinging some trades to diversify a bit, but I have to agree with the consensus, it doesn't really seem to matter.