The suit had a Force Field, which he could polarize to generate magnetic attraction. He also was able to use the armor's sensors to create a "chameleon field" around himself; the armor's computer would analyze its surroundings and generate a hologram to make the armor blend in with the surroundings, making him effectively invisible.
His weaknesses were the interesting bit: Silver Centurion was mostly solar powered. He'd constantly run out of power at a crucial juncture and would need to recharge from electrical sources like a simple power point. But if he couldn't find a power plug somewhere he'd be able to convert heat and cold to power the suit.
It's also interesting to note that a copy of the Silver Centurion armor was used by Tony Stark to defeat the Mandarin, when his Extremis abilities were temporarily deactivated due to concerns with his mental health.
With all that going on, it would be hard to not recognize Iron Man no matter what armor he wore--the Iron Man visage had been burned into my mind's eye because of this armor. And I didn't even like Iron Man back then!
After having seen so many versions of Iron Man armor in the comics, and now the movies, looking back at the Silver Centurion suit really brings back a sense of a simpler time, when a more powerful suit of armor came with drawbacks that were just as powerful, and where some triangular shoulder guards meant a more kick ass modern look.
Placed side by side with the newer armors, the Silver Centurion probably looks out of style. But as a toy, it shapes up like the classic it's meant to be. More after the jump!