I dont like the fact that if you do get a puncture with tubeless then you have to get your hands covered in liquid latex taking the tyre off, the rim strip off (if you dont have tubeless rims) then put a normal rim strip on and then a tube in and put the latex covered rim strip in your jersey pocket.
You know you don't actually need rum strips? Not running any on non tubeless rims, don't know of anyone who needs to. If it goes wrong enough to have a proper flat then the sealant is mostly gone, I remove the valve and put a tube in. The valve goes into one of the safe little pockets on my camelback.
I see the point about tyre swapping but with the exception of DH I tend to run the same rubber for at least half the year by which point it's either dead and needs changing or it's winter and needs changing.
I swapped the tyres on the missus XC bike (TR rubber and TR rims) in about 15 mins with a track pump, syringe or the little stans bottle to hoover up the sealant and a quick spray with the fairy liquid and it was all back up and running.
I was skeptical at first but properly converted. Don't run low pressures normally round the 30-32 mark but find when you get to 40psi it's all a bit too skittish anyway.
As for the downsides I've had 3 riding issues,
2 were landing sideways/scraping the tyre into a gully/rut which would have don'e bad stuff to a tubed tyre too.
The other was casing something very badly onto a rock, that would have popped a tube too.
After that I decided to put some more air in while waiting for a race start and panicked and bent a presta valve core. I had the thing sorted and back up with a tube in under 5 mins.