I have seen the rules for encumbrance and they actually make slightly more sense than previous versions of SR. However, I have not seen anywhere, no matter how hard I look, any weights listed for any of the equipment!
Am I to take it that a character with Strength 1 can carry a gyro-stabilized Panther assault cannon while wearing Full Body Armor? The only weights/masses I have seen anywhere are the average weights of the various metahumans.
Is this an oversight? Or did I merely get an incomplete, unrevised rulebook? Or is everything weightless?

Rules say: Within reason.

Strenght 1 w/gyropantherarmorofdoom is not reasonable.

Strength 1 with a heavy pistol and a lined coat IS.

yeah, the book gives guidelines about how much weight you can carry before you are encumbered, but the GM is apparently supposed to decide when you've reached that limit. so, basically, check with your GM.

And I'm happy, because frankly, Who really enjoys keeping track of gear weight? I'm a hard core number cruncher rules lawyer, and I ususally skip it.

Yup, same here.. tho I wouldt call me hard core..

I am the GM! I've got a lot on my plate without having any guidance from the rulebook. Luckilly, I remember some of the weights from previous editions, but people new to SR may not realize, even approximately, how heavy some of this stuff is and therefore what is considered 'reasonable'.
Sure, I never forced my players to track their encumbrance to the gram, but it is handy to at least have a general idea of how much, say, a Commlink weighs.

I'd trust the reasoning of a streetbum strung out on crank before i'd trust SR3 weights.