I am a huge fan of using photoshop/aperture plugins and presets. I think they allow you to work much faster, provide repeatable approaches to certain looks (for unified portfolio's) and they're just plain fun to use. My only reservation with plugins (I'm probably weird for feeling this way) is that I don't want to ever use them to the detriment of my vision. Does that make sense? I've really tried to make a push in my photography where I try to think through to my processing and the look and feel of the final image before I even fire my camera. I know some people don't work in this manner, but it's slowed me down and made the photos that I do take, much more purposeful. I like that.
With filters, there's this tendency to click through the presets till we find one that we like and then that's it. The preset has just decided the final outcome of the photo. I don't like that idea. It takes the vision away from the artist and puts it into the hands of someone else. Make decisions!!! Use the filters. I do constantly, but work them, their sliders and presets around your vision rather than your vision around the filters. PS - Now's as great a chance as ever to tell you that my favorite plug-ins by far, are the ones created by Nik Software. Hands down, they are the best plugins available.
All of that said, let me tell you one of my favorite exercises for strengthening and building my focus while using plugins and presets. When I am making a black and white image, I usually make at least 3 conversions. I use Color Efex Pro 4's conversion, then Silver Efex Pro 2's conversion and then I usually will do a black and white adjustment layer in CS5. (And if I'm really feeling crazy, I'll do a few more...) Technically, if I am working towards an idea in my head instead of letting the plugins make all the decisions, then even though all the conversions were done in different ways, the resulting layers should be relatively similar. Sometimes it's crazy how similar they come out! Then, I mask together my favorite parts from each of the conversions into a master image that I feel is exactly what I imagined!
Sure, it may be nerdy... But it's stretching me and my thought process and also my post processing to be intentional with the images I take and what is produced afterwards. I like that.