This seems like a reasonable request to me;  I'd like to see a little bit of convergence between the float and Decimal APIs.

One difference between the two types that's worth noting is that the float.as_integer_ratio() method can never take a ridiculous amount of time or memory, whereas Decimal.as_integer_ratio() could:  e.g., consider Decimal('1e999999999').as_integer_ratio().  But I don't really see that as a problem.