Eric Poolewrote a review of Cervelo S3 Disc Ultegra Di2 R8070 Complete Bike on October 2, 2019
Familiarity: I've used it several times
Let's face it, aero is in when it comes to features that are desired on new bikes nowadays. I made up my mind a while ago that a few watts saved here or there based exclusively on aerodynamics doesn't mean a whole lot to me, especially if it comes at a cost of comfort in the saddle. That is, until I spent some time on the S3..
Upon picking up the bike, it felt a little weighty, probably on the side of 8.6 (ish) Kg. that's a rough estimate, not weighed on a scale.
Hopping on the bike was a whole other story. Saddle & geo felt extremely comfortable - carbon layup felt stiff in the pedal strokes, with not a major difference from other carbon bikes when going over harsh(er) gravel. No complaints about cockpit or touchpoints on the build - aero bars were fine when my hands were on the tops during climbs. nothing fussy with the internal seatpost. Internal wiring makes the bike look exceptionally clean, and not having floppy wires aids to its' aero claims.
Ride quality was pretty fantastic overall. I found myself grinning ear-to-ear on flat sections, as I was riding 2 - 3 mph faster without notice. Descents felt extremely fast & confident through corners, disc brakes only accentuating that confidence in late braking. Build kit was stellar, Ultegra Di2 NEVER failed in all shifting - even when testing some front shifts under load. I didn't necessarily feel like I could "dance" up climbs as well, but every pedal stroke provided excellent power transfer - making it a candidate for hilly or even mountainous terrain/climbs.
I'm 6'3" weigh 170 (ish) - rode a 61cm build. Felt very comfortable and could probably take some spacers out if I wanted. If I wanted to go full race mode, I would size down to 58cm.