When I first got it I was surprised because it isn't as heavy as you think it's going to be, but it has enough weight that it sits well in your hand. It weighs 669g, so a lot more than a Switch, but then it is much larger and far more powerful. And can emulate Switch games.

The 2 touch pads under the thumbsticks are something I've not mentioned. They are full trackpads just like a laptop has, which is really useful in games that use a mouse and in desktop mode, but they are also multidirectional when you push down on them too, like a dpad, in addition to clicking them down as a mouse button. But they are also heptic, so as you move your finger over them they give you sensation feedback.

You also have the gyroscopic 6 axis controls like you have in a smartphone and dualshock controller, so can set it up for movement when you move the Steamdeck around in a FPS. In a handheld this works really well because you are holding the screen up and moving around literally pointing directly at targets like a camera.

The Steam demo built to show off the Decks controls, called Aperture Desk Job, really showcases all of them to not just show how they work but reveals some that many won't realise exists. And you can fully customise the controls per game.

The 4 back buttons are a very useful addition; having access to some more because some PC games do utilise more controls than a standard controller can offer. When you first use them they feel a bit awkward as you logically push directly on them into the back. They do work like this, but they also work if you squeeze them towards the hand grips in the curved part and that's so much more comfortable and less awkward. And as you say, you could reasign an L3 or R3 click to one of the rear buttons if it's easier to use.