On the topic of the knock, I have seen some people complaining that theirs does not always work properly, sometimes getting stuck in an ultra-extended position or refusing to retract. The same mechanism is used on pens from Karas Kustoms, so it's not a problem unique to Tactile Turn. While the knock is quite sturdy (and nearly silent!), it does involve moving parts and thus will wear out with enough use. If this is the case, you can buy a replacement pretty inexpensively here.
I have also experienced click malfunctions on occasion, but I find that taking the pen apart and flipping the included spring around usually solves the issue. I think that sometimes it just gets caught up on something and needs to be repositioned and usually after that small effort the pen works smoothly.
While you can find numerical measurements for the size and weight of each pen on the Tactile Turn website, I find that the aluminum Mover feels very similar to writing with a Pilot Vanishing Point. They are roughly the same size and weight, so if you are a fountain pen user who is fond of the VP, this might be a good option for you. Even if you prefer lighter fountain pens, most people can get away with a heavier gel/rollerball/ballpoint pen because of the different writing mechanism, so don't let the heavier weight discourage you if you otherwise really like this pen.
In terms of the rest of the writing experience, that depends heavily on the type of refill you use. I have used the guts from a Pilot Juice since I received this pen and I really think that it is one of the best gel pens you can buy. It writes very smoothly, especially with the heftier body of the Mover behind it, and all the colors are well saturated, waterproof, UV proof, and available in pretty much ever color you could ever want. That being said, there are plenty of other refills that will fit, so check the website for the full list and see if your favorite is on there.