I really haven't. Strangely, the rational, analytical part of my brain is telling me it should be fine (because they are trustworthy and the likelihood of issues of any kind is very small), and I would say it's the other part the says to think about it more. Seems like it should be the other way around, right? And it's not because I have reservations about them, per se, it really isn't, it's more that it's opening our closed network, and once you open it, it's no longer closed.
And, fwiw, my main motivation is really relationship-building and neighborliness; while savings is always nice, it's not the main reason I'm considering it (though I think savings, and also less hassle, is why they asked).