My experience is good. I use a pair of Thule Thruride 565s which don’t require adaptors to accommodate different axle sizes or widths – between my MTB, CX bike and road bike I have 20mm, 15mm and 12mm thru axles. There is also an adaptor that comes with them for a QR.
The bit I like is that the bikes are really stable on the rack and without a front wheel attached are (arguably) less attractive to the walk by thief. I say arguably because the only evidence I have is that I haven’t had a bike stolen from the roof.
The downside is having to place the wheel in the car. I have never failed to find room for a wheel and I have a couple of wheel bags for those post muddy ride situations. I am not sure there is any benefit in fuel economy over a wheels-on roof carrier.
I also have a Thule 561 wheel-out carrier which was a lot of a faff with different axle sizes but if you only have one axle size its as good as the 565 in terms of holding the bike firm.