In theory, it shouldn't have any problems, provided the Rosetta emulation software is doing its job properly. It simply won't perform as well as a Universal binary would, because all of the code is being run in a virtual machine which emulates the PowerPC instruction set, which means that for every instruction the computer needs to work out how a simulated PowerPC would interpret it and react.
All the reports I've been hearing suggest that PPC apps run very well under Rosetta and it is stable and reliable, however you should keep in mind that a universal binary version of the app will typically be four times faster than the PPC binary.