seventy one, greetings; To implement my suggestion certainly may require some planning and adjustments as you allude to. However my point is that one can best determine the virtues and vices of any item best by using it rather that listening to the opinions of others. It should not be construed that running two separate OSs would or should be a permanent policy, but rather a method to determine which suits the OPs needs the best.
As I'm sure you know, some applications run only on Snow Leopard. In such instances, there may be features that are resident in subsequent OSs that a user might find attractive thus dual OSs may be the answer. What ever suits a users needs is fine with me. I have no strong feelings one way or the other.
On my primary MBP I run Lion only. (I would have Mt.Lion but one of my wireless ISPs is not compatible with !0.8)
On my secondary MBP I have Snow Leopard as the primary OS with Lion and Mt. Lion in smaller volumes for test purposes. I have not committed to Mavericks yet. I gladly let others blaze the trail. 🙂
Best regards.
Ciao.