Roller nuts.....
 

.....anyone got one on their guitar......especially a Tele. How do you rate 'em?

I've worked on several, even installed one on a Strat. They are excellent as far as playability. It takes some work to get them adjusted right. Usually have to work the slot a little to get them low enough.

They are most useful when you use a lot of trem bar - not so useful on a Tele.

I’d rather have a good bone nut with slots properly cut for the strings.

I can appreciate that the slot would need more work on it....are they adjustable for height once fitted?

Why not so useful on a Tele?

Have one on a Strat. It’s not bad. Not sure that a tele without a whang bar needs it, though...

Pendant warning: I'm going to Fender's now conventional missuse of the term tremolo...

On Stratocasters one can bend pitch down with the trem arm (in fact some set up their Strat so they can only bend down). This slackens the strings, and if taken to Jimi Hendrix-style extremes it's possible for the strings to get hung up in the nut. Some whammy-abuse Strat players whose guitar are set up with floating trems (so they can pull up and raise pitch) kind of automatically give a little upward wiggle on their trem arm after a pitch dive to try to make sure the strings don't stick.

Roller nuts help prevent this, though a well-cut and lubed conventional nut and other fixes (like graduated tuner posts height to eliminate string trees) also fight this problem.

Telecasters don't conventionally have tremolo bridges. Of course you can bend stings up with blues vibrato, and even do pre-bends and release for pitch drops. There are even extended techniques used by some players (twisting the tuner key, bending the neck with force while holding the body, or pressing the string above the nut). While up bends can also hang up in the nut, it's slack bends, bending down in pitch, that have the greatest risk. This is the same reason that beginners are often reminded to always tune up to pitch when tuning their guitars.