It is clear, that transmutation circle in FMA plays significant role for transmutation result. I really doubt, that, for example, Isaac McDougal can use Mustang's circle for water transmutations, and vice versa. But during Brotherhood series, there several example of usage of same transmutation circle for different goals.
First example - Alphonse circle. For instance, aside of creating things such as cage for Paninya, in Liore he also manages to fix radio (which is fairly complex device) with same circle.
Another example is Roy Mustang, who was able to use his circle for at least two really different transmutations - his common attack with burning oxygen in air, and dissipating water to hydrogen and oxygen during first encounter with Lust under fifth lab.
So, question is - how important is pattern of circle, and is there any hints, what variety of transmutations are allowed with single circle?