All trainers take time to warm up, but about 5-10 not 10-15. And no, during warm up it's not that big of a deal (you're also warming up, remember

).
As for the knobs, if the handle is plastic it's okay as long as the inner parts, where it actually touches your skewer, are from metal (which i'm sure they are). Otherwise most trainers have plastic outer knobs and handles.
And since I dont know anything about the cyclops magneto, I cant comment on that. I own a Mag 850 myself, it's magnetic and LOUD (got it before fluid trainers came out, or atleast before they were affordable

).