Shadowrun being described as D&D meets cyberpunk is like saying Cherry Coke is just like regular Coca Cola except with a cherry taste. It gives an idea but is wildly inaccurate at the same time. SR4 rules are nothing at all like D&D, and they are very playable and consistent. To my way of thinking, a rules set provide all the meat and about half of the flavour of a game. The setting has the other half. The setting for SR is a distopian future Earth where gargantuan corporations have as much or more power than national governments. Yes, there are orks, trolls, dwarves, elves and humans, magic and cybernetic (and biological) augmentation...but it this doesn't mean it's cheesy. Well, OK, that last bit is my own personal opinion.
And yes, it can be very VERY dark. After all, the primary occupation of the player characters are criminals who live outside normal society, and work as deniable assets for people and organisations that need something done or someone taken care of. I like how you can be contracted to provide support to a starving vampire philantropist one day, providing discrete protection for the illegitimate son of a Russian Mafia don while he goes trick or treating on Hallowe'en, and working to kidnap a nuclear scientist from her safe gated community and transporting her to another country (against her will) the next night.
Actually, SR4 can be as light or dark as your GM wants to make it.
I've used a modified set of SR rules to play on Harn, and it was my most successful campaign.