Good, bad, otherwise?

I prefer them. Easier to install the pump head and I expect they reduce the wear and tear of the rubber seal in the head.

For many years, until just the past several months, I would say no difference. Lately I have had a rash of tube failures (both thd and non-thd stems) at the tube to stem joint on what I formerly found to be quality tubes. I may have to rethink my position and try that nut.

I like Michelin Ultra Light unthreaded, never had a defect or flat at the base of the steam.

Thanks for the opinions.

I just received an order of several tubes from Nashbar, missed the fine print where it stated they were threadless, first thought they were seconds, as I hadn't seen/noticed threadless before.

Good........

have used both. Can't say I've had a bad experience either way

I use the smooth band just below the cap thread to engage the silca pump head gasket so it 1 saves wear on the pump gasket
and 2 makes it easy to pop the pump head off when Im done ..

Sewup tires the stem is glued to the rim with the tire so pushing the pump head onto the stem is resisted by the glue..
the ring nut serves that function on a clincher tire when tire completely deflated ..

some obcessing posters, here, seem hate the ring nuts as 'too much weight' ,, they may be happier with out the ring nut threaded stems .

Not too much weight at all, just unneeded and another delay when repairing a flat. Also, ever get a new tube where the nut was cross threaded right from the factory? I did and discovered it while changing a flat on a dark cold morning. Fortunately I had another tube with me but I've always discarded the nuts since then.

Untreaded:
Look cool.
Sometimes more difficult for a pump to grip onto.

Threaded:
Not so cool looking.
The dorky kurl nut on a threaded stem can keep the tube from ripping while inflating with a pump. You don't push the valve into the wheels as much.
I've had long valve stems make a clicking noise. The dorky kurl nuts stop that sound.