Not to take anything away from Nintendo, props to them for finally moving in a better direction with online stuff, but that's a much smaller sample size both in terms of number of games released with online functionality and the online player population. While there are big failures like Driveclub and Master Chief Collection, the majority of games with online features work reasonably well right out of the gate or at the very least are largely fine beyond the first 24-48 hours or so of servers getting hammered.
Unless you're really hyped about the limited functionality that's currently been shown off, you probably shouldn't buy them. If you just want a cool Nintendo character figure, there are a lot out there that are far cooler and not that much more expensive.
I'm already pre-ordering far fewer games than I was a just a year or two ago, but that is largely just due to my game purchases becoming predominately digital - Amazon is fast but downloading is still faster.
That being said, I don't have any intention of ever cutting off my pre-ordering / pre-loading completely. I'm going to keep on buying into games that I think are worth buying into, where my interest and base-level confidence in the developer/publisher outweighs any feeling that I need to wait for reviews and early impressions.
Most games are just available for one month and then are gone. Occasionally some will carry over (Chariot has been free for two months, I think), but you shouldn't count on it. You don't need to actually download it though, you just need to go through the process of "purchasing" it so that it gets added to your account.
Mostly no. Still can't accept people into the Xbox One clan. I can see all of the applications, and @rolyatkcinmai or myself will accept them if/when it's ever possible. If you somehow managed to slip in during the short time when the app was working, you probably now appear in the clan in the game.
I'm not sure how exactly we're defining "well regarded", but Civilization: Beyond Earth is a game that did pretty well critically that I (along with many other Civ fans) found to be quite disappointing. It's not a terrible game by any means (though it does have a lot of fundamental issues), and it has the potential to become much better if supported with further expansions. However, with Firaxis coming off of some amazing games in Civ V and XCOM and invoking the classic Alpha Centauri, there was almost no way this game could live up to the expectations.
Also, I really liked GTA V, and I'm likely going to buy it again.