Another Quadlock user here.
It may well be the best out there but still far from perfect IMO.
Mine lasted ~2 years before the phone started wobbling around and falling off if you weren’t super careful. The (replaceable) lever part had worn really badly. Replaced this and then noticed the quad bit was worn as is the phone case so looking at having to buy another complete set at £50+.
The waterproof cover does a good job of keeping water and mud off the phone but makes the touch screen unuseable when it rains. It also covers the speaker so if your using voice guidance for following a route you can’t hear the directions and can’t unlock the phone to see where you’re going without stopping to take the cover off. I wouldn’t bother paying extra for it to be honest. Phones are pretty water resistant these day anyway. Get a silicone plug to keep the crap out of the charging port though.
I use the out front mount but fitted backwards to mount the phone above the stem. Works OK. The mount looks and feels quite flimsy which is disappointing for the cost of the kit. When it’s new though, it does do a good job of holding the phone. It’s sturdier than it looks.
Rather than replace mine with a new Quadlock, I’ve been looking at the SP connect but haven’t found too many real world accounts of how well it works. I like the fact that it’s all alu though and they do a topcap mount which you can’t get with Quadlock.