I have only heard of them from friends talking, but you raise a good question.
I think before they are released into the wild, we have to be absolutely sure that these modified mosquitoes won’t mess around with our ecosystem in any way we haven’t planned. Of course, this is difficult to know in practice, and lots and lots of testing and modeling will have to be done.
But if scientists can say “There’s a 99.999% chance that nothing unexpected will happen” then yes, I think they should be released.
I actually hadn’t heard of this, but I think Mark has given an excellent answer: we need to be very very sure that releasing them isn’t going to have a catastrophic effect on the ecosystem that they’re part of, but if we can be pretty much certain of that, then yes, I think it’s a good idea.