1--i see alot of good results with the magic filters, but from what i understand if you want to take topside photos between dives, you have to take the camera out of the housing, and pull the filter off the lens. Is this true, and are the filters a one time use type thing.
Actually, I did some experiments with the Magic Filter for topside photos out of curiosity, and the same concept for white balancing applies onland as underwater. Even with the Magic Filter on while between dives, if you simply do a white balance, it neutralizes the extra red for surface photos/videos. In the few land photos I took with the filter on, I didn't see an extra red at all. The filter comes in a big enough square that for a small P&S you should be able to get 4 different pieces from it.
2--I've also read they that the magics are basically a red filter, so would i be better off just buying a red filter, or some other type of filter to fit over the front of the housing.
I found that the Magic Filter really becomes quite useless below about 60-70 feet, or in any dark areas such as in a cavern or under rocks - often where the really interesting critters dwell. So if you can afford the extra housing and/or adapter, the wet lens concept (where you can add/remove underwater) seems ideal. But certainly for most diving situations, the Magic Filter is quite an inexpensive and easy way to go IMO.