Did this on my Meta 5 – it's slightly stiffer but not hugely.
Flex wasn't a major problem with my frame but I think they have changed the swing arm since.
I went for the Maxle route for convienience and I had Hope Pro 2 hubs, so just needed a new axle/conversion kit.
Not sure if I would pay to do it again, but I would look for a maxle on the rear of any new bikes I bought.
hope that's useful, sorry if it's a bit vague!
I would like to make the switch on my Coiler – with 2.5 tyres I get rub on the brake arm when cornering and pedalling. like you, it's the cost/hassle that is putting me off.