Though this is a UK site, I'm adding a review for these tires because there aren't any reviews yet! Hope this is helpful for anyone considering these :)
These Falken Sincera SN250ASs are the OEM fitment on my US market 2017 VW Golf Sportwagen Alltrack with the 205/55R17 tire fitment. I have run these tires for 19,000 miles through mixed commuting conditions, taken quite a few spirited drives on twisty mountain roads, and with the tread about ~60% gone, I took the car up to the mountains for the first time recently and got a taste of their capabilities in snow and below-freezing temperatures.
Overall, despite my skepticism for all-season tires AND OEM tire choices, these tires have quietly impressed me with their overall dry grip, feedback through the steering wheel and seat, and the overall feel when you push them. Turn-in is great, but yet mid-corner adjustability somehow manages to shame some UHP summer tires I've had within the last several years on other VWs (I'm looking at you, Continental ExtremeContact DW). The tires give plenty of warning through the wheel before giving up grip, and grip levels seem very high for an all-season tire.
They don't seem to give up very much in the wet either, though you couldn't claim wet performance is their STRONG suit. Feedback and the progression of grip are still excellent in the wet, but aquaplaning resistance feels pretty average (I mind puddles with these tires more than others I've driven, but I don't fear them like I have with some...) and the compound doesn't always bite into the road that well so wet handling can feel a little "greasy" at times. My limited experience on snow also bears out the fact that, while this is still much better in cold than a summer tire, you have to be careful with speeds, braking distances, and turning on these tires. It's hard to tell how much better these tires would be in those conditions at full, brand-new tread depth, but I can tell they would never be that great...the compound is hard and it feels hard for snowy conditions.
Noise comfort from this tire seems average; tire noise is a little roaring and would probably be more pleasant if the pitch was lower, but it's not something I notice in the car unless I think about it. The ride comfort over bumps is a little brittle, but well-controlled in the sidewall on the rebound to help give the car a taut, confident feel.
At the current treadwear rate, these tires will easily go past 30k miles, but 40k is probably a stretch. 35k seems likely. Given my driving style, I would expect 20k-30k out of summer UHP tires depending on brand (I've had good luck getting 30k miles out of Michelin UHPs, but less from others), so getting an extra 10k miles of treadwear and a M+S rating (important in the US for snow chain control restrictions on AWD vehicles) without trading much dry weather feel or grip is actually a really great compromise for my driving style and use in California. I have also lived in Washington state and while these would still be a good choice there, I would probably pick something a little more wet-weather focused there.
Overall, this tire is a surprisingly sporty tire hiding in a rather innocuous looking all-season tire, and is actually a really good choice if you value the combination of dry grip and performance feel, a little cold-weather grip for occasional snow use, and decent-to-good ride comfort, noise, and wet weather performance. It's a narrow niche between a good UHP summer and other all-season choices, and pricing is a touch steep at least in the US, but I've been quite pleased with this tire over my time with it and if you can find it for a few bucks (or pounds) less than a competing Michelin, Bridgestone, Continental, etc., it's worth considering!