Nagaoka Dust Roller...Best or Worst Thing Ever?

I have a roller made by Nagaoka/Rotel that appears to be amazing, but I'm not sure about risks that might be related to using it. It looks kind of like a lint roller, but the surface is made from a soft tacky-feeling material that attracts dust and is washable.

It is apparently soft enough to form down into the grooves and pick up the dust in there, which it seems like it's really doing. After brushing a record, playing it, and then using the roller and playing it again, there is a definite reduction in surface noise. There's no residue left behind, and you can wash the dust off of the roller with a little soap and water to completely restore its tackiness.

NOTE: I have a normal wet/vacuum cleaning process that I use to get the deep-groove crap out, and I use a carbon-fiber brush in my regimen as well. The Nagaoka Roller is not a substitute for "real" cleaning, but it seems like it might do a really good job between cleanings.

Has anyone here ever used one of these devices?

Never used one, but I will now after reading your post. Sounds a lot like the washable, soft, tacky-feeling lint rollers you can get at Walgreens for $3.00
I have one and find that it does leave a film. I use it though, as part of my wet cleaning regime. Record gets a quick clean with the carbon fibre brush, followed by (if it's really dirty) a roll with the Nagaoka, followed by a wet clean. This simply gets a lot of crap off the record before it even receives a wet clean so as to minimize contamination of the felt vac slot on my KAB.
I have had my Nagaoka cleaner since the mid '80s and it still works perfectly - the squishy material on the roll is sorbathane. I do not use it for its intended purpose, however, because it leaves a film on the record. I use it for used records before subjecting my record cleaning machine's velvet slot to all the dust on newly acquired used records. I also use it to dust the acrylic platter on my TT periodically. I keep it clean by running it under hot water, then letting air dry. Do not use any detergent on will end up with a lot of film on your vinyl. I didn't realize this thing was still made. Where did you get yours Dusty?

I found it on eBay. I had read somewhere about it, and it seemed like a really good idea in theory so I wanted to try it out. It's used, and I'm really happy with it so far. It looks like with proper care it will last for a very long time.

I like the idea of using the roller as a "pre-wash" step. It does a good job of removing film and dried up fingerprints that sometimes don't come off even with aggressive washing. I haven't noticed any kind of residue left behind after using it. What kind of light to you use to see it?

The film can be seen on the flat lead-out groove area near the label. My room lights are halogen spots. I also have a goose neck incandescent over the RCM. Can be seen in most bright lighting though.
I use mine exactly as Hdm described, to remove loose stuff dredged up by my Hunt CF brush before wet cleaning. My Nagaoka also leaves a film, though it cleans off easily and seems to decrease as the roller ages.

Highly recommended convenience tool for removing loose dust and cat hairs, provided you wet clean and vac afterwards.
Yeah, I use a gooseneck halogen over my workstation now (as of yesterday) and I can see the residue. VERY slight, and it easily comes off with the scrubbing and vacuuming.

How deep, in millimeters, are the grooves of a record? Wouldn't the roller only need to be able to flex that amount to get down in there?