I've used grips without tape for half a year now with no problems. I have golf pride +4 tour velvet midsize grips.
I used to put blue masking tape under the grips and I noticed the twisting at the ends as others have mentioned. But now, I use no tape and just stick the grips right on to the steel bare shafts. If ya think about it, as long as the grips aren't way bigger than the shaft and are made of decent rubber with some tack, they're not going to slip. There's a lot of surface area between the grip and the shaft to provide enough friction as long as you have a decent quality grip and it's the proper size for the shaft.
A good test is to install the grip and then see if ya can pull the grip off. When I first put grips on, there's a little slippage because air is still between the grip and the shaft but if ya give it some time, the air escapes and the grip will stick securely.
If you grip the club tightly and/or there's lots of twisting action in your swing, the no tape method may not work for you. I recently started gripping lighter (as many instructors advise you to do and I gained 5-10% in yardage and increased height in my ball fight) so no tape works just fine. Plus, changing grips is really easy. No tape, no solvent, no muss, no fuss. I air compress the grip off using a needle, and then pop a new one on. Set the preferred alignment, let the air settle & escape and it's ready to go!
An additional note, I do not use tape on my woods & driver which are graphite shafts and I have no issues with slippage or twisting.