I personally think Starmer is doing an ok job, bit non-descript but he's making BoJo look like a blithering idiot in PMQs (not hard admittedly) and is being generic enough overall, for the time being... Whether he'll do enough close to the election is the real question.
It's clear that politics in this country is so short term and blinded by spin essentially, BoJo/Tories are doing well in polls right now because of the vaccine success which has almost nothing to do with them, and the 'corruption' is being ignored. But that's short term and in 2024 or whenever that will be long forgotten and it really depends on the politics at the time and how well Starmer is dealing with them.
To actually answer the question, I'd be inclined to vote for them today really, I've historically been a Tory voter although I almost didn't vote/spoiled my ballot last time (doesn't help that in my area only Tory, Labour and Lib Dems bothered running, I would've voted Green if possible based on the last election) but given the current governments clear and unabashed corruption means I will definitely not vote them next time, and maybe like an ex-miner I might never vote for them again
But, the area was Lib Dems pre-coalition and has been very strongly Conservative since, so it doesn't matter.