Yeah I saw yngwie a while ago and it kicked ass.
He is alot faster than people give him credit for (people don't seem to realise that he rarely plays at his fastest). He's still way faster than petrucci and romeo.
He plays scale patterns in a similar way to the jazz greats; unique picking patterns that are normally, amazingly, improvised.
And if that's not enough, he plays scalloped frets that apparantly totally screw up your playing if your left hand technique is not perfect.
Probably the only area where I can genuinly say he has been surpassed on is sweeping; but then again his straight minor/major sequenced sweeps are his style, and he could probably play outside this area if he wanted to (infact sometimes he does, like the sweeping in seventh sign).
His vibrato is perfect and his playing is filled with emmotion. I love the 'stream of consiousness' style his solos have - they are normally not in a defined structure and this is something that has influenced me in my own playing. Alot of the time he doesn't even play in time - the solo just floats over the rhythm section yet it always ends in the correct place.
His solos pretty much defines the 'speed = emmotion' thing (was it Al Di Meola who said that, I can't remember). When he plays something fast, it isn't a planned excercise, it is a buildup to something awesome. When he plays an ascending run it just sounds like an explosion of music.
I went through a phase of thinking people like MJR were better (although I didn't want to admit it) because of all the crazy tapping/sweeping/legato stuff they do. But then when I improved alot at guitar, I realised that stuff is actually pretty easy to play (no disrespect - it sounds awesome and takes great skill to write those original modern sounding phrases) in comparison to the stuff yngwie does. Once you have sweeping and tapping down, it's so easy to overuse it because it looks and sounds hard, and neglect what is actually the pinnacle of technique - fast picking.
One last point: people who say that yngwie is sloppy (and I see it written alot) are talking total shit. They just don't know how scalloped frets are supposed to sound. How the hell do they think he gets away with playing on an acoustic? He doesn't really write many good songs though, which is a real shame. I think something like stratovarius with yngwie as guitarist could be insanely good, just sucks he won't work in a creative environment with other people.
People comparing him to fusion guitarists - yes those guys are awesome, but I wouldn't say they are *that* much better than yngwie. The way in which they improvise over constantly changing chords is insane yes, but
1)They have learnt in that style. That's how they have been 'raised' on guitar.
2)Most of those guys have a good ten years on yngwie. Guitarists at this level are improving all the time
3)When people are this fast it really is hard to say who's faster. What You can say is that they are all in the same ballpark. I've seen videos of both McGlaughlin and Di Meola improving for like an hour mostly on acoustic, and theres nothing they did which made me think 'wow, yngwie couldn't do that' - save the 'improvising in no particular key' and being able to play for so long without doing the same thing twice. Technique wise, they are in the same league.