393 Motors: Fairly good. Some better protection at wire junction would be nice. Overall a decent low power motor with convenient compound gear reduction and mounting threading. Very good for low power general purpose robotics prototyping. The reason you might hear about negative reviews is because a part of VEX competition is about working the motor as hard as you can without them tripping current in the 2 minutes of game so your robot moves faster than anyone else’s. So the 393 motors take up a lot of beating in VRC, but I suppose the same will happen even if VEX allows more powerful motors. There’s been many test by jpearman and others on the motor; you can go look them up to make your own judgement.
VEX Cortex: Way overpriced. Nowadays you can buy a pi for 20 bucks or cheaper, with more computing power and memory. I’d say from a non technical perspective that the memory of the cortex is not big enough for very serious computing work. But it is very very convenient for teams. All of the hardware and software compatibility issues are reduced down to almost none. I’d never buy a cortex for my own projects. Some Arduino board or some pi computers would be a lot cheaper.
Joystick: Overall very robust and reliable. Never seen one break. I’d prefer slightly bigger joysticks, but everyone seems to be fine with them. Three power options (battery, AA chord to cortex, charger) make the product ideal for testing and practicing. But is indeed very overpriced.
LCD Display: Overpriced, but a good product. You can use the screen flashing as an additional feedback signal, and you can do some seriously useful programming work with those displays and three buttons. It is noted that the buttons tend to bust after some heavy use.
Aluminum parts: I would probably guesstimate that 90% (?) of structural components in VRC nowadays are aluminum parts. The aluminum parts appeared as a substitute for old steel parts. They are weaker than steel, but a lot lighter, which allows teams to use higher base gear ratios to drive around faster. Way way overpriced, but a necessity in VRC. The overall design of the product is great. Making good pre-manufactured frame parts is what VEX is good at, and they make a lot of money with this skill in FIRST. The strength of the material satisfies majority of VRC competition needs.