Fisrt off, let's consider the 240v here, and there ( other countries)
Our 240V is hot to hot, theirs is hot to nuetral.
Not a big deal, as long as their is a third grounding connection, and no connection of their appliance's nuetral to ground.
If the appliance is a resistive load, not a big deal to go 50 to 60 hz. If it's inductive, motorized, the conversion just makes it run a tad slower or faster, depends which side of the pond your on.
I say this having viewed the converters travelers use, it's simply an X-former.
Ok so far.... please speak up here, i am no authority, this is pure speculation from me.