I remember staying at the Pusat Belia one time and the Capital Hotel the other...back then the only places that were even semi-affordable. Am sure there's more choice now. The two big mosques are impressive, the water village was worth a stroll and of course the Royal Regalia Museum (including that life-size march replica in an air-conditioned hall).

Didn't get to see Jerudong Park or the national park, but I'd prioritize the latter if it's more easily accessible now.