It feels like you're stepping on a solid block; there's practically no travel at all. And even with the soft springs it requires a lot of pressure (the spring you use changes the amount of pressure needed to hit maximum, but it doesn't change the pedal feel at all). My Playseat Challenge wouldn't be up to it if I hadn't bolted the pedal board to a piece of plywood and fixed it to the pedal tray. The build quality is very good, but it's let down a bit by the worse build quality of the Logitech pedals themselves, which flex and creak under the strain.
That said, it is easy to brake consistently with it. If I close my eyes and try to hit a particular brake percentage, I can usually do it. It also responds well to very light taps on the brakes in a way that's a bit more difficult with the stock springs.
But from an aesthetic perspective, the 923 stock brake spring has a nicer feel, and it feels more like a real brake pedal.