I write this review from a cardboard box infront of my old house. Had to sell the house, both cars and pay out my life insurance to afford a rig that can run MSFS at descent FPS, however still a good deal. Nothing beats seeing my (former) home in MSFS and flying circles around it - not even the real thing, so it's not a bad deal that I'm homeless now. The cardboard box is not too cramped and the new owner of the house was so kind to grant me free power for the 3000W power supply of the new PC and free WiFi for the next 5 years, and one shower per week with the water supply for the garden. Hopefully none of the 4 GPUs will fail from the moisture inside.
I don't miss the real world, I now have it all inside my new cardboard home. I just hope the rain doesn't leak inside...

Now, for some real stats.
[email protected] stock, GTX 1080, 32GB RAM, game files on an older SATA SSD.
FPS on city airports with lots of 3D models of buildings around: average 27-35, average flight around 45 FPS, flight over the sea around 55 FPS.
Load is very heavy on GPU, not CPU. My 1080 is at 100% load 80% of the time, CPU is at ~30%. This is for High-end settings, not "ultra".
Playing without SSD is nearly impossible, also the download takes around 10 hours till the ~120GB are there, because Microsoft throttles its downloads to around 40Mbit/s - my connection is a solid 100Mbit/s. This has caused some problems for people with slower connections because the game download for them takes longer than the Steam refund time. However other people report having much higher download speeds, it just seems to vary.
So far, no other game is that heavy on my PC. Squeezed out a few more FPS with MSI Afterbruner for the 1080.
While an internet connection is not needed, it is recommended since the terrain textures are actual satellite images from Bing Maps, and depending on how populated the area is it looks pretty nice. Microsoft has introduced 3 major updates for MSFS so far, 1st for Japan, 2nd for the US, 3rd for the UK. These updates include high-res textures of cities captured via drones, and they definitely look better than countries that haven't gotten an update/upgrade yet.
Still, even the "normal" geodata looks pleasing for purely procedurally-generated regions.
Plane cockpits look absolutely fantastic yet lack some functionality which you might be used to from VATSIMs.
Also features a live weather simulation, so if you don't like the outside world, you can just uninstall your weather apps and use MSFS instead. Weather can be adjusted in a very flexible way, multiple cloud heights, wind speeds, temperature - which affects ice effects on the plane wings/engines/windshields.
The challenges present at this time are truly challenging, depending on your hardware. While I had a HOTAS for a few days for testing, i usually just use an Xbox controller, but even that one has a sufficient analog resolution to precisely place my plane on course for an approach. Chances are, that you'll use ILS for big airliners anyway, and the smaller planes react quickly enough to feel nice with a controller - given you re-map some buttons to the controls you desire. Not as reactive as GTA 5, more like Arma 3.
Yes, it's relatively expensive and yes, it needs permanent internet for good textures, but overall my experience has been overwhelmingly positive. Some of the custom modders charge a little much for the planes/airports/content they made, but in general it's worth it if you like a certain plane/airport.
I feel like in 5-10 years we will see a number of other games that reduce local files by loading textures/models via internet depending on where you go.