I would have sold it as long as you have something else, just like I sold my 5700 XT for £600 (I bought it for £450) during the mining craze, just because I found a 2070 for £500. That's £100 in my pocket for nothing.
I
want the card more than I need the £200 I could profit by flipping the new GPU.
As an SI I am never short of alternative hardware - there's a dusty 2080Ti and a spare 4060Ti sitting on a shelf next door right now, but I won't be able to get a 5070Ti alternative right now. I might still flip it on eBay when the 9070XT comes out. I like having two desktops with both an AMD and Nvidia GPU under the same roof so that I can always see the experience for myself in real-time, but this 5070Ti isn't undervolting as well as I'd hoped, so it's probably not a candidate to replace the 4060Ti 16G in the HTPC which needs to be near-silent in a very specific, and not particularly well-cooled case.
What I have a word against is the recommendation to buy a product based on the fact that "there is nothing else available in that segment at the moment".
It's not really a recommendation, in the same way that I wouldn't recommend people buy a 4080S or 4070Ti Super. That level of performance is a long way off the performance/$ sweet spot and I still think the 7800XT at £470 today is the best option for an overwhelming majority of gamers looking for the sweet spot. If you can get a 4070S for under £550 or a 7700XT for under £375 those are also awesome choices. All three of those cards will run a game well, at high details, high refresh or both and allow you to get the full experience from just about any game that's out right now. Beyond a certain point, improving the graphics hits diminishing returns and if the game is good it's unlikely to be good because of the graphics.
My point was that even an £850 5070Ti is objectively, measurably better performance/$ than the 7900XTX, 4080S, and 4070Ti Super. The price of 40-series cards has gone back up to silly money again in the last month because all of the supply has dried up and the flagship AMD card was never a good value in the first place.