[Larne]

Having recently upgraded to the 40D I was pleased to discover that it has two modes, one shooting at ~3 fps and the other at 6.5 fps. Most of the time I find the 3 fps is fine but I did find the 6.5 fps useful when (for example) I was trying to catch a wave breaking against some rocks and wanted to catch just the right moment.

I guess what you need to think about is just how fast what you are shooting is going to change. Or rather, how long is the window in which it is going to stay the same? If the scene you want to capture is likely to remain relatively static for 1/3 of a second then a 3 fps camera will do you fine. If you are looking to capture a fleeting instant then you need the highest fps you can get.

Having said all of that, I would recommend buying the best camera you can afford. The speed in fps is just one part of that equation and the more money you spend the better performance you are going to get in a wide variety of areas.