Apologies, this became a bit of a tome, and I share your quandary.
I'm a big proponent of informed choices and data-driven expectations. To me the critique of cars is a fundamental prerequisite, and if there were forums on roller coasters then I would read it (btw, there is.. h
ere,), though the analogy is inaccurate as this is the customers, not the park owners or maintenance workers - you give us all too much credit on here. Armed with information, I have can set my own expectations that is driven more by data and less by unencumbered enthusiasm.
As an early owner of my p85d there were definitely things I wish I knew now vs. then which would have guided me better and grounded my initial expectations - however, as many have said being an early adopter is a conscious decision that's based more on emotion than available data.
We ordered a production ModelX quite a bit earlier and have it awaiting configuration. One of the earliest sig owners in our area kindly brought their X to an event after I requested and that helped - though there's still no way I'm going to purchase one without driving it. Thankfully just another couple of weeks before we have 15 minutes driving one.
In terms of faults, issues, etc. It's fair to say that you won't find many people posting "Wow, my car was amazing and had no issues", that's just not the nature of online forums... silence is usually happiness!
Rather, when asked, I've heard no owners who would wish for anything but a Tesla given a repeat purchase. This level of evangelism appears to be primarily due to the satisfaction with Tesla and their ability to think differently, eg. completely voluntary seat belt recall that affected (afaict) 1 car mistake from the entire fleet. Tesla didn't try to hide an issue, instead they announced it proactively, sent early notification for self-test, set up service appointments, and even had staff at the Superchargers to do this proactively for minimal potential inconvenience - never heard of this type of customer sat before. I have many other examples, though you get a flavor hopefully.
Should you expect the 1st generation of ModelX to be perfect? No.
There will be niggles and you should expect these. The service centers are great, and will try to accommodate you to minimize inconvenience, though TM appear to be selling cars at a faster rate than the rate of increase of service centers.
Should you expect continual refinement based upon experiences in the field? Yes.
Again, compare an early Model S sig to a p90D today and it's amazing how much better fit, finish, etc, are.
Additionally, we know that Tesla enhances the vehicle capability in software wherever it can (you don't find other car manufacturers doing this). When this requires new hardware which are "easily" retrofitted they have done so - examples I've taken opportunity for are 3G to LTE, and Ludicrous upgrade for original p85d owners. Other examples are more extensive and not available, or cost ineffective, eg. autopilot and 85 to new chemistry on 90 battery.
Only things which some believe are coming, though unknown when is the corner and/or rear-facing radar for enhanced autopilot. I can't imagine this will be "retro-fittable" unless the wiring harnesses are in place.
Am I buying the X? If I didn't have my current p85d, or this was a replacement car, given my experience to date: Absolutely, Yes. Though as this is the replacement for my wife's ICE car: still unknown. Ask me in a couple of weeks, post test-drive.
Good luck, hope this helps,
Cheers, Mike