The good:
A fairly gritty combat system which nonetheless doesn't make every game a slaughterfest. Interesting rules for magic which make it seem that little bit more 'real'. The feel of the gameworld, and the amount of possibilities it offers (there's very few campaign styles which would be impossible while remaining within the world of SR). Artwork - it's cool. Australia! It's there! And it's written by aussies! Adventures and adventure paths which are useable and interesting.
The bad:
Character generation takes quite a bit (primarily due to spending resources - personally I'd make up some 'package deals' for the next time character generation is needed). Some of the available adventures assume that your team of materialistic mercenaries will just decide to be heroic for the hell of it...
The ugly:
Inconsistent mechanics - SR lacks a core mechanic like d20 has, and I think it hurts it. New players will take quite a while to find all the little nuances which apply or don't apply from situation to situation, and typically distinctions made serve no real purpose. Vehicle rules are awful - lots of unnecessary complexity, which leads to unplayability and some truly bizarre scenarios. Layout - someone really needed to point out to fasa that the equipment section is NOT the place to put rules on armour stacking, just as an example. Now that wizkids is doing things, layout seems much better.
As for doing SR using d20M? Unless you seriously alter the combat rules for d20m, you won't get the same feel. In SR, almost every fight is decided by who has the superior position. In general a fair fight in SR is a no-go. In d20m, you'll really fight to scare your players without just killing them all.