Rotary converters are fine, however you just have to be aware of their limitations.
Some equipment won't tolerate a big mis-match on voltages, but even your mains 3 phase is rarely perfectly matched. You're only likely to get problems if the false leg is majorly out of tolerance, or you are pushing equipment to it's limit.

However some rotary converters leave a lot to be desired in terms of controlling the false leg, and safety protection.