Easily my favorite keyboard form factor of all time. It has everything I need and nothing I don't use (and layers for things I want but don't use often). It's small enough to slip into my carry-on bag for work trips, or just in my backpack for when I'm going to chill at a coffee shop.
Construction-wise, the Preonic Rev. 3 is built like a tank. Make sure you save the tiny pamphlet in the box, it has the assembly instructions. Personally, I go for the ultra-secure plate method. This uses the provided bolts and spacers to make the plate firm within the case. The plate is a hefty stainless steel plate with a tight tolerance. It will take some force to push the switches in.
BE WARNED! The hotswap brackets for the switches can come off if you push too hard. I have made 4 of these model and have never had the issue, but it has been known to happen. The recommended method is to put a few switches in the plate, then line them up with the PCB, then place the remaining switches in place by putting your finger on the back of the PCB to hold the black hotswap in place while you use medium force to push the switch into the plate. This reduces the risk of popping off a hotswap.
The board is programmed with QMK, but make sure when flashing it that you use the Rev 3 firmware. Rev 2 used a different micro controller and the firmware and layouts aren't compatible. I would love to do a write-up on QMK, but it's a bit complicated to set up and there are a million different things you can do with it. If you have questions, you can always ask on the OLKB subreddit (reddit/r/OLKB). Search first! Your question has probably already been asked and answered, but if you're really not sure just make a new post. People will usually help, but it's not super active so it may take a day or two to get a response.
Included is a picture of my collection, which is just about a year old. I have quite a few more now...
This is my first orhtolinear, and three days in I'm really liking it. I'm still in the process of figuring out where I want keys to be, and am _really_ liking the MOD_T setup (i.e. left-shift on hold, enter on tap, etc).
From what I can see, it looks like there is a little solder on the USB-C connector, though that piece still makes me a little nervous. I got a magnetic cable set ( https://amzn.to/2Eup4dR ) so there isn't any strain on the connector. Since I pack this from work to home and back, it's great for the convenience factor alone.
The board comes with presoldered addressable LEDs around the edge of the board, other than that there is a cutout under each switch where you could put LEDs but there is nothing else other than the hole. If you wanted per switch LEDs you'd have to wire them separately.