Sound - The biggest pro about this guitar is that it produces the Iommi sound (of recent years) extremely well. I have had the oportunity to play Black Sabbath songs with this guitar through a Laney 100 watt half stack, and it's a blast. The sound is dead-on with Black Sabbath's Renuion album of the late 90s. Tony's dino heavy rhythms and the piercing lead tone are right there. Through Marshalls and Orange amps, the Iommi sound is also quite convincing, though slightly less authentic than through a Laney. It also does AC/DC and Mountain type tones very, very well.
Pickups - The sound of this guitar is 100% due to the excellent Iommi Signature pickups. Hi output pups that crunch well while retaining definition. They clean up beautifully when you roll back the volume, and are very quiet at high volume.
Neck - It's a decen't neck. Comforatble. Compound radius, I think.
Iommi-specific mods - 24 fret neck, smooth 61 style neck joint, Sperzel locking tuners, graphite nut, and cord jack on the bottom edge of the body rather than on the face are all nice touches.
Appearance - It looks cool as hell. It's the only SG I ever had a jones to own. The cross inlays are sterling silver. Unlike the cheaper Iommi models, these crosses are of differing sizes, proportionate to the surrounding frets -- just like Tony's. These crosses undoubtedly gave Gibson an excuse to jack up the cost of this guitar.
Tuning - Despite the high cost, it's still an SG, and as such, it is succeptible to all the issues SGs have, such as whippy necks. The most aggrivating thing about this guitar is that it doesn't stay in tune well. Even with the Sperzels, it never seems to just settle down and stay in tune. I find myself re-tuning after each song.
Workmanship - when you pay this much for a guitar, the workmanship should be FLAWLESS. It wasn't. It arrived with volume pots that would not take the volume all the way to off. I replaced them. The fretwork is good, but not stellar. Again not commensurate with the price.
While the inlay work on cross inlays is done well and cleanly, the crosses are sterling silver which means they tarnish over time. You have to polish them up to keep them looking great.
I don't find the two extra frets usable.
I bought this guitar (in 2002 I think) pretty much knowing it was way too expensive for what it is -- a slab mahognany body finished in one color (even if it is a nitro finish). You are paying a LOT for aesthetics. Still, I thought it was the coolest looking SG I'd seen, and I figured it would be a useful studio axe and a fairly good investment guitar. It was a good studio guitar, but when I sold it years later, I only got what I paid for it.
However, if all you need is the sound, I'm convinced you could drop a set of the Iommi pickups into any decent SG (Gibson or other) and get that same Iommi sound for a lot less money. There's just nothing beyond the pickups about this SG that contributes to that Iommi sound that isn't available with any other SG.
The sound of this guitar combined with the quiet pickups make it a very good studio axe, particularly for tracking rhythms. If you're in a Black Sabbath tribute band, you could not do any better than this guitar through a Laney. It looks and sounds the part perfectly, however, I've found the lack of tuning stability to be an issue I'm not sure I'd want to gig with.