the 540's are MTB pedals... I've run that type of pedal for nearly 20 years... as far as durability they are hard to beat, they are also easily adjustable and because of the dual sided nature they are easy to get in... if you aren't riding in mud/clay that could easily gum up the pedal/cleats they are a great way to go for a first set of clipless... if you want you can save a bit more $$$ and go with the m520 and spend the extra on shoes http://www.nashbar.com/bikes/Product...67_-1___202530

I've never used the m324's, I can see the allure just to hop on the bike but I know my a520's (single sided with a platform for extra support) can be a bit of a pita to get clipped into when pulling away from a light quickly... my old dual sided I never had to even glance at the pedal to clip in.

that being said... spend more then you think you want to on shoes... good shoes make a huge difference, find ones that fit well and have a good secure retention system, but as with all shoes make sure they fit properly, different brands fit differently, it seems Italian guys have skinny feet... some shoe makers put lots of room in the toe box and others not so much, you just have to find the shoe that fits you correctly

also cycling socks to wick moisture are a great addition for footsie comfort... you can get em cheap (expensive compared to your typical socks) but they can make a huge difference in comfort.