Very sturdy, especially the pedals. I sit on my living room couch and my G29 is supported by a Wheel Stand Pro. The combination is great.
The Driving Force GT that I used with my PS3 is just a toy in comparison to the G29. This is a proper simulator tool. I played hours of Project Cars and F1 2016 on my PS4. I noticed how easy it is to catch those slight overseer moments. With the game pad (same PS4 games) or with my old Driving Force GT (PS3) I had to set up all cars to understeer a bit so I wouldn't lose the rear end on corner exits. With the G29 I get great feedback that allows me to set the cars up to be more neutral. In combination with the great throttle pedal modulation, my corner exit speeds are faster than ever.
The brake pedal has great feeling. It is just like a real car (albeit not a race car, but how many "normal" people would have the leg strength for that?). At the end of travel, it becomes hard, simulating the brake pads touching the discs. You can very easily go hard braking from high speeds and slightly pull it back as the car slows down so the wheels don't lock up. I am playing without any brake assists whatsoever and have full control. I brake with my left foot and agree with another comment that the the brake/throttle are too close together for this kind of driving, but it would make no sense to right-foot brake an F1 or Le Mans prototype when in real life the drivers use the left foot (as they have no foot clutch). It was tricky to find a good sitting position with the Wheel Stand Pro's column on the way, but like the other reviewer I moved the pedals slightly to the left and it feels great, even though I'm 5'8" and my legs are aiming towards the center more than someone taller who could move the pedals further forward.
The paddle shifters are sturdy enough and do what they're supposed too. The "clicking" sound doesn't bother me even though my speaker volumes are low, but I can see how some people could be annoyed.
I don't have the stick shifter add-on and have never used the clutch, so my review doesn't cover them.
My only negative comment is the "clipping" you get when the wheel simulates extreme situations (like driving over certain curbs), which is a consequence of this not being an actual steering system linked to actual tires. Some calibration can help with that (lots of info on the Internet) but I found that the default settings provide the best compromise, as clipping removal tends to reduce overall feedback under "normal" conditions.
If you're a car person and/or racing fan that enjoys simulation driving, you'll be happy with the G29.