Hey Balsamiq gang,
I once said “If I won a billion dollars, I would buy Balsamiq and make them implement search and replace”. So it goes without saying that I’m enjoying this feature. 
I have found one bug. When searching and replacing in “exact match” mode, occasionally the “find” text is not replaced; instead, the “replace with” text is appended to it. Oddly, this seems to happen almost entirely inside Comment (yellow sticky note) containers. It may have something to do with the text being adjacent to a period. For example, if searching for “one” and replacing with “two”, I occasionally get a result of “onetwo”. It seems that once I searched for “one” and it replaced an instance of “one.” with “one.two”, but I may not remember that correctly.
Anyway, hope this helps!