Yeah, when I play leads, which is pretty rare, I do that almost constantly, I like the sound so much. First heard it used a lot by ZZ Top and been using 'em since. All the time.
Actually I use it quite a lot for chords as well; you can get a lot of chord variation by playing full chords for instance from down to up instead of right way, or for instance using pinch harmonics towards the end of the sweep etc.
Some sounds and/or guitars aren't as easily squealing...you can do it even on acoustic or clean sounds, but to really get them to squeal there has to be enough gain, yeah.
Dee
"When life's a biatch, be a horny dog"
Amps: Marshall JVM 410H w/ Plexi Cap mod, Choke Mod & Negative Feedback Removal mod, 4x12", Behringer GMX110, Amplitube 3/StealthPedal
Half a dozen custom built/bastardized guitars all with EMG's, mostly 85's, Ibanez Artwood acoustic & Yamaha SGR bass, Epiphone Prophecy SG, Vox Wah, Pitchblack tuner plus assorted pedals, rack gear etc. for home studio use.