I'm British, married to my American wife. Docs received email: April 5th. Priorty spouse app. Still waiting as of today(22nd). With recent bank holidays, only been 10 working days technically.
One thing I would draw everyone's attention to which will not be obvious to Americans yet to fully experience living in the UK, is the following: The 8th-23rd April is when all kids are off school. Young professionals like me without kids who continue to work through this period notice a huge difference in the traffic. It feels like the country shuts down. A lot of parents take their holiday leave, often going on holiday abroad. They get fined if they take kids on holiday inside the school term. I do not expect that the UKVI Sheffield office of ECO's are immune to this. Not only that, but Visa fees jumped by 400 dollars as of April. Priority fee also jumped 100 dollars. It is reasonable to expect that there was a jump in applications received from people who were aware of the fee increase and had planned to avoid it. So what I'm saying is, of all the months in the year that will be distorted in terms of processing times - April would be it, due to the perfect storm I mentioned above. Come the 24th April, I would expect the Sheffield office would have a full team back in place and we can expect to see processing rates return to what are expected, but bearing in mind they may be returning to a backlog of applications with a lot of catching up to do!
Of course this is still a guess, but I would contend it is at least an educated one. Oh how I wish an ECO - current or former, would show up on these forums and give the lowdown on what goes on inside that office!