The ones that are very expensive are definitely good glass. The ones that are medium expensive are also definitely good glass but more common. Some of the ones that are dirt cheap are definitely good glass but are cheap because every camera came with one (50mm f1.8 For example). The rest are the cheap other lenses which have a slightly more mixed review - most of the zooms, but as they're cheap go buy one, try it out and form your own opinion. As "walkabouts" I often use zuiko zooms, and I am seldom disappointed. The only one I don't like is the 35-70 f3.5-4.5 - the small one. Much prefer the 35-70 F4.
Detail from the 35-70 F4. No such thing as bad Zuiko glass!