Technique & chops - Scarratt came in as the hot gunslinger replacement of longtime Saxon guitarist Graham Oliver. The band needed someone to contrast Paul Quinns' more 70s' style chops and lead work, and Scarratt stepped up the plate and than some. Scarratt has monster chops, sexy vibrato, flash tricks and all.
Taste - Despite possessing a high level of technical mastery, Scarratt is also a very tasty and mature player who always plays for the song and enhances it with his leads, mirroring the feel of the song. He can motor, milk sustained notes, and even throw you off with some modal-fusion sounding run that'll give the song a new spin. There are some exceptions during live solos where he might resort to some picking wankery, usually when playing over Olivers' old parts.
Diversity - You probably wouldn't guess it from listening to Saxon, but Scarratt is actually a very varied and diverse musician. Prior to working with Saxon he was a fairly prolific session-man, earning his bread in the pop and fusion market. I would recommend trying to track down a copy or purchase an MP3 one of his collaboration with Saxon drummer Nigel Glockler, Mad Dogs & English Men. Stylistically, It's somewhere between Lukather/Satriani/Aldrich, tempering equal measures of fusion, rock and metal. Very cool stuff.
Recognition - As with his partner in axe, Paul Quinn, and the band Saxon in general, widespread recognition seems to elude Scarratt. Not many people really know who he is and there is very little information on him around. No one seems to care enough outside the hardcore Saxon fandom, and it is a true shame. He is one of the more interesting and diverse players in metal today, and most people haven't got a clue.
Rhythmically, Scarratt brought some more modern metal sensibilities in his riff writing, broadening the sonic scope of Saxons' sound. It's all very grounded in old-school NWOBHM, nothing out of place mostly based on root 6 and 5 power chords and some arppegiated folk chords. His album with Glockler shows more variety, showing off some fairly offbeat and cool rhythms you'd more likely hear on a Jeff Beck or Steve Lukather outing. In both vehicles it is evident Scarratt has a very ballsy rhythmic approach, as Saxon albums have been ripe with heavy, ballsy, cool riffs since he joined, more so than before.
Leadwise, Scarratt has all the gunslinger chops and attitude you'd want. He's got an overall very confident command of the instrument, much higher than that of Paul Quinn. His solos almost always sound composed and are very well structured, reflecting the feel of the song and complimenting it very well. And for all his technical skill, Scarratt is just as passionate and fiery as his partner in axe, Paul Quinn. A prime example would be the lead break on State of Grace off of The Inner Sanctum. Scalewise it's mostly Aeolian, Ionian, Minor and major pentatonic. You get some diatonic scales every once in awhile, mainly in his album with Glockler. His work as a sessionman would indicate he's atleast somewhat schooled.
Doug endorses Dean guitars and has a signature V Dean model, along with playing various other Deans like Dean Hardtails, Custom V's and the USA 84 Moden exotic. Lately he's also been using a Gibson Les Paul Custom with floyd rose like Paul Quinn. He's also been cropping up with the ocassional Ernieball Musicman. Scarratt uses Marshall amps.
Doug Scarratt, like Paul Quinn and Saxon, is sorely underrated. He's an extremely diverse and capable guitarist, with alot to offer musically. I highly recommend paying attention to his work, he's got a distinctive style that is easy to tell apart from Quinn. Saxon got alot more than I believe they bargained for with him, and so would you if you give him, and Saxon, a good listen.