I've used a 3/32" for a little over 2 years now. I've only had one chain break (a SRAM, I didn't use the masterlink). Since then, I've used Shimano 8spd chains with their pushpins.

Now, the more that I think about it - I should have used the masterlink on that SRAM - you're never putting backpressure on the link - so there's no reason to think that it would come apart - your chain is always tensioned - even during backpedalling.

My friend runs one - he just finished a tour on his fixie from here to Florida - no problems, and he has had it on his bike for a good while before this tour too.

I have broken 1/8" chains on my pedicab - 4 in the last six months. Nothing is unbreakable.