Stuffed this in my running vest for a half marathon and barely noticed the weight. Once it's empty it flattens down small enough to shove in a pocket, which beats carrying a rigid bottle.
Avery★★★★☆
The bite valve really does let me drink fast without stopping, which is exactly what I wanted for race day. Only gripe is it takes a bit of effort to get the last sip out when it's nearly empty, but otherwise it's been solid.
Timothy★★★★☆
Fits nicely in my running vest and barely weighs anything when full. The bite valve takes a couple sips to get used to, but once you do it's quick to grab a drink mid-run.