I have a cheap WD Green M.2 installed on this computer, and the boot timer reported by Task Manager is 11.2 seconds. Not that young of an installation too. You'll see changes everytime you move up in the hierarchy unless something bottlenecks, but it will be a bit less compared to one before. For me it was 62 seconds on a 7200 RPM HDD, then 23 seconds on a SATA 3 SSD, and 11.2 seconds on the M.2. There is a few notes of caution for this and also some ways to speed up without investing in a new part though.
1)Check with your motherboard manual. Motherboards a) sometimes don't support M.2, b) sometimes support up a to a certain size, c) support it but disable something important (like SATA ports) at the cost of it. Also make sure the keying is correct and you still have the M.2 standoffs (or just order one with it)
2)Try diagnosing the PC first to see how far you can go with the current setup. Simplest is to disable unnecessary startup tasks from Task Manager (You don't really need Spotify to start up first, do you?), and more expert is to log a boot using Process Monitor and see what takes the longest time in a boot. You can also set up the pagefile (make sure it's bigger than the RAM) and sleep the computer instead of turning off, which will make it boot WAY faster when you press the button. It consumes a little power in that state though.