If you absolutely have to shoot at ISO's above around 800 and output your master at higher than around 720p then you might want to use some sort of grain removal technique. I did a variety of tests over the last couple of days and I came up with the following answers. There are a variety of plugins and aftermarket tools for grain and noise removal. In one way or anoter I tried the following.

DE:Noise FxPlug for FCP, FCE and Motion by RE:Vision FX. It works well and can be used directly in Final Cut Pro or in almost any other finishing solution. It costs around $150 and did a great job but it is sloooow. But as I soon found out almost any other grain removal techniques are guaranteed to take a long time as well. I also found some problems with some fake plasticy remnants on some of my footage as if something had a secondary color correction on it that didn't key quite right.

In After Effects they have a remove grain effect which works really well. It comes with the Pro version and has a multitude of settings. It seemed like this approach took longer than the FCP way with the DE:Noise plugin but like I said you would have to let either one of them go over night for even a minute or two long clip. Apparently the AE plugin is derived from what used to be Visual Infinity's Grain Surgery.

I tried the built in noise removal tools in Combustion but I did not have much luck. In my opinion the one found in After Effects worked much better and definitely has a lot more options. Overall removing grain is doable and offers great results but takes FOREVER.