elementk wrote a review of Sea To Summit Ultra-Sil eVent Compression Dry Sack on May 25, 2014
Familiarity: I've used it once or twice and have initial impressions
Haven't taken it on a trip yet, but it seems great so far! Super light, strong, and completely waterproof. I tested it with toilet paper in the sink and it kept it bone dry. Basically, it seems like a lighter-weight version of the 'old' e-vent sack.
Here's a more thorough review that I posted on Imgur: