So I don't own one of the Fanatec direct drive units but my pedals (Clubsport v3) and Shifter (sq 1.5) are both Fanatec units. The wheel I use is a Accuforce V2. My first wheel was a Fanatec Porsche Carrera wheel that I used for years, it did have issues but I learned to deal with them and those issues seemed to be Windows related. I imagine the Fanatec DD unit is very nice and comparable to my Accuforce in the learning curve to getting them to act they way you want them to.
TLDR: Their equipment is far from perfect but treated well and maintained well they have served me well. Support can be good but slow in my experience. I feel sim equipment requires a bit of tender love and care to keep it functioning as it should.
Anyway, to my point, both my Pedals and my shifter are great pieces of kit if taken care of. They stand up to abuse fairly well but basically require maintenance to keep them running well. Knowing my experience with them I would steer people to higher quality units if they can afford them and if not tell them about what I do to keep them running right.
With the pedals I have to lube them up every couple months with the supplied lithium grease. This keeps things feeling smooth and not squeaky. The screws holding the sensor for the throttle like to back themselves out causing erratic readings and the bar holding the clutch in place likes to slip out of place. I've had two items replaced to do with both of these issues. I keep an eye on the screws for the throttle sensor, checking them visually and through the Fanatec property page each time I lube up the pedals. I do the same for the bar in the clutch that likes to slip, there is a small hex screw that holds it in place. Now that I know to check and maintain these things frequently I no longer encounter these issues while racing.
As for replacements I had to have the original throttle sensor replaced, it stopped functioning
properly, Fanatec Support was helpful and sent one to me for free(within warranty). The bar that the clutch pivots on (right behind the pedal) likes to get loose and backed out. The original bar wouldn't go back in place, I think it was warped from slipping out of place and then enduring my foots wrath. Fanatec was able to ship me one, also free of charge. I made sure to use loctite on the hex screw when I put in the replacement.
For the shifter there is one small problem that likes to pop it's head up about once every 6 months to a year. Luckily it is easy to fix but it is particularly annoying to encounter in a race. There is a small metal magnet that sits in a slot within the shifter. When this gets moved slightly in either direction you will encounter miss shifts. Usually I have found either shifting into first reads as reverse or shifting into 3rd reads as first. This can cause you to blow an engine or at least have a nasty spin in game. It is very easy to remove this magnet, put a little loctite on it and reposition it centered using some pliers and a screw driver. I have gotten in the habit of opening my shifter up every third time I do my pedal maintenance to check and see if the magnet has moved at all. Usually it hasn't now that I put loctite on it.
So to summarize the gear is fairly nice and works very well, especially compared to cheaper offerings but requires maintenance. I really wish Fanatec would include some sort of guide on how to maintain their kit, better than what's in the small manual that comes with it. The pedals were easy enough to figure out but I had to look up my issue with the shifter online to find the solution. I suppose if your stuff is in warranty you could send it to them if you encounter an issue and you probably should. Personally I don't mind learning how something works and how to maintain it and warranty was already gone by the time I ran into most of these problems.
I think of their gear similar to how I think about working on my real cars. If you care about it you might as learn how to maintain or fix it. Also it's worth coming up with/following a maintenance plan for mechanical things. I'm a bit old school, I keep a log book for my cars and my sim gear. I don't mind having to do this maintenance, I've even done 'car days' where I change the oil on a car, maybe a couple other things and then do the maintenance on my sim rigs pedals. If anything, I do wish it was built just a bit stronger but I can't really complain for the price paid. You get what you pay for.