Ok, lets keep this simple kids, there's no point arguing over whether or nor root of all evil is good or bad. how you're going to like this album depends squarely on which Arch Enemy singer is your personal favourite. If you're into Angela and her sandblasting death metal voice, then you'll probably like this a lot, as some of us are of the opinion that the song-writing was a bit better on the older albums. Likewise, if you thought Johan was a crap vocalist there's a good chance you too will enjoy Root of All Evil. However, if you liked Johan's approach then be prepared, as Angela's atonal roaring has none of the desperaion or emotion Johan had. As such, i think it's really impossble to say whether or not this is a good album, and how you like it will be totally subjective.
It's really that simple, because in terms of the songs themselves there's hardly any difference performance-wise between the originals and the re-recordings. Although some songs seem a bit slower to me (e.g silver wing) but it could just be me. The more modern sounding production is the only real difference (maybe the rhythm guitars in are a bit higher in the mix then the originals), but its pretty negligiable. Again, its a subjective thing that I can't say is good or bad. It depends on where you stand in relation to the band, and if you've already got the originals you're probably better off sticking with them unless you really want to hear Angela on the old tracks.
So there you have it. If you're an Angela-phile you might like to add a star or two, and if you're a Johan-lover then you might want to take away a star or two.