I am a copywriter by profession and therefore write a lot. My old keyboard gave up the ghost after ten years, so I had to look for a replacement. It might cost a bit, because I'm a professional user, but I didn't have the budget for more expensive mechanical keyboards and was specifically looking for a combination of wireless keyboard and mouse with an easy connection.
My eye quickly fell on the Logitech MK545. The form factor seemed nicer to me than the slightly more expensive MK710; the MK545 has straight lines, a no-nonsense layout and a uniform, black color. The additional control keys (volume control and pause/skip) are also subtle on the MK545, which appealed to me more visually. The MK850 seemed slightly more ergonomic, but I didn't need the function to switch between devices that you find with that set, so it wasn't worth the extra cost.
A nice side effect of the MK545 that other reviewers mention is the battery management. Keyboard and mouse have no battery and are therefore not rechargeable, but both use AA batteries (so you don't have to keep two types in stock) and go through smart energy management 36 resp. 24 months per set of batteries. I have yet to see how that works out in practice, but other reviewers confirm its longevity. The fact that batteries are included is also very nice; so you can get started right away.
Installation is as simple as plugging the USB dongle into your computer. Keyboard and mouse are immediately found, recognized and installed. Takes less than two seconds. By installing Logitech Options you get access to extra functionalities, but these are limited with this set. I have also noticed that input lag sometimes occurs since I installed the Logitech drivers. This was not the case during the previous days. If you notice something similar, you can consider removing the drivers.
My further user experience is positive. Compared to my old set, the keys do feel a bit spongy, but in my view that is mainly a matter of getting used to. The ergonomics are fine. The mouse does what it's supposed to do and fits comfortably in the hand, even for someone with large hands like me. Other reviews complain about the build quality of the mouse, but I have to admit that I like these a lot better than the mouse I had.
All in all, highly recommended, especially if you're looking for a practical, no-nonsense set for use in the (home) office.