What's your stack and reach?

I've tried it (and the E-117+) and loved both. Stable and comfortable.
Previous bikes were a Felt DA4 (2013-2015) and Kuota KueenK (2009-2012)

Really liked the rear brake not being hidden under the BB and the extensions that tilt.

I upgraded from an sworks shiv to an E119. I appreciate the integrated Di2 routing. With my setup, there's only a few inches of cable exposed. The integrated brakes are clean and not bad to work on once they are setup. There's a graphic floating around that it beats a P5 at +5 degrees and wider in the wind tunnel.
As for fit, it's very adjustable.
If you go for e119 over the e119+ you can choose your own integration of fuel, hydration, and flat kit. The e119+ is stiffer and without the add ons, is a 110 grams lighter. Either way the e119 is stiff and light enough. I haven't had any issues yet. Called Argon customer service once and they were quite responsive.
If it helps, I can shit on my old shiv. Two recalls on it (seat post and aero bars) left me out dry for than month. Specialized's customer service isn't bad, but I'm disappointed they weren't more prepared with the recalls. The di2 integration was terrible. With Tri Rig parts, I was able clean up the front end. The bladder was cool though. I miss that.
What other brands are looking at?

Thanks very much
Speed Concept 9 series is the 'safe' choice
E-119+ is the left field option

Why didn't you buy the Speed concept and still consider the E119 ?!