So my iPhone 3G was starting to feel very sluggish - I could literally start counting the seconds off between clicking on the Safari or iPod icons and when I could actually do anything in either app. Didn't remember it being this slow, but I thought it might be just me justifying to myself why I needed a 3GS, especially since neither powering off and restarting nor clearing the Safari cache didn't speed it up. But then I tried loading and force-quitting
all the apps I use with any regularity, particularly Safari/iPod/Mail, and it has dramatically sped up the loading of each of these apps (based on the time-honoured method of counting off "one-Mississippi" between load times).
I wonder if that means the iPhone apps could be hogging some resources, even if they don't seem to be running? Well, whatever works.