You know, I've never had an issue with my 20-year-old steel frame that I've ridden in all kinds of weather for years in terms of rust. And I'm not the most fastidious. I did give it a powdercoat recently, but that was more aesthetic. I wipe the bike down occasionally. The rust danger has always been more theoretical. The main thing I like about my alu frame, though, is acceleration at intersections.