Bradley Aaron Wiltfong
I ride a 2017 Propel Advanced SL 1 (https://www.giant-bicycles.com/us/propel-advanced-sl-1-2017).
I, personally, love the bike. It is stiff, responsive, and unapologetically fast. The ride is not as harsh as some other aero bikes I've ridden (venge, foil), and it seems to absorb the bumpy roads we encounter around here more or less in stride. Definitely doesn't belong on gravel or very rough pavement though. Being an aero bike, you are sacrificing a little bit of weight for speed, but it still climbs adeptly. The longer wheelbase compared to a traditional frame gives it a secure and stable platform on screaming downhills or spinning it up on the flats. The overbuilt headset and bottom bracket also plays a role in the stability of this frame at speed and provides for great power transfer and road feel. That comes with downsides though, because the headset is oversized it doesn't fit standard sized aftermarket components. You'll be stuck with Giant forks/stems/spacers. It sports a press fit bottom bracket, so that comes with its own set of pros and cons, but I have not had any issues outside of the standard breaking in period. The frame geometry forces you into a more aero position which can be a bit uncomfortable if you are unfamiliar with it, but this is common for aero frames and I expect you are comfortable in an aggressive position. Wind wise, that mostly depends on you as the rider. I weigh 180lbs and have never had issues. I come from Kansas where wind, not hills, is the defining feature of race courses, and never felt unstable. Yes, you feel the surge and can be pushed, but you won't get blown off your line or knocked down. It cuts through headwinds like butter. It is competent and stable in corners, but lacks somewhat on the responsiveness that more traditional crit frame would have. It sprints like a beast though. Power transfer is off the charts and it loves to be thrown around.
A few notes worth making you aware of:
1. The most common criticism of this bike is the brakes. They are a mini-v brake that require a non-negligible amount of regular maintenance. I check them before just about every ride and am tweaking them regularly to ensure the best tension and alignment possible. I have them rebuilt once or twice a year to clean and restore them to perfect order, this is a required piece of maintenance. They can be annoying, but the braking power is phenomenal and I have never felt unconfident with them. The criticisms arose from the early models of Propel with Giant brand brake calipers. There were design issues with the springs and body that lead to them being sticky and unreliable. All new propels come with an updated TRP version of the brakes that solves those critical issues. You do not need to buy expensive aftermarket brakes.
2. The teardrop tube shapes make affixing rear lights and fenders difficult. Keep that in mind.
3. The tire clearance is a bit lacking for a modern frame. Granted, this is a pro caliber race machine, but it would still be nice to fit larger tires. 25c is generally fine, but not all brand's 25c will fit. Shwalbe Pro One 25c does not clear the chain stays under load with that minimal amount of wheel flex that is inevitable. 28c is absolutely no chance.
4. Everything is internally routed. If you do all your own maintenance, this may not be the best frame for you, but what aero frame doesn't have this issue?
5. Another improvement starting with the newer models is the bolted on front derailleur hanger. Previously, it was braised on, and coupled with early high torque di2 front derailleurs, could be pulled out of the frame, totaling it.
6. Front and rear dropouts are bare carbon. I prefer alloy plates in my dropouts, for long term durability, but I have not had any issues yet. Just be careful when taking wheels in and out and don't over tighten.
Finally, the coolest thing to note is how my average speed changed when moving to the Propel. Previously, I rode an Sworks Tarmac, and upon switching I noticed an automatic gain of 2-3mph average just for free. The aero benefit is real, and it is a lot of fun to cruise at 22mph with the same power levels that only got you to 19 previously. All in all, whether or not this bike is a good fit for you largely depends on the type of rider you are, and what you are looking to get out of it. This is a performance bike. It emphasizes speed at the cost of just about everything else. It is not the bike to go cruise on. It is for hammering, and that is where it excels. It can do everything, but there is definitely a niche where it performs best. If you are a weight conscious rider or have a traditional climber build/strategy this may not be the bike for you. If you are a crit racer who dives corners, forces gaps, and relies on nimble responsiveness, it may not serve you best. However, if you like hammering out turns on the front of a paceline, mixing it up in a group sprint, or going for that solo or small group breakaway, you're looking at the right bike.
Hope this helps in anyway. If you have any more questions or whatever, feel free to hit me up.
Brad