Kona I've gone back and forth between SATA and IDE a couple of times and honestly, it's not a big deal.
Sure a smooth-running SATA will be a little smoother than a smooth-running IDE, mainly for huge files such as DVD or DVD temp files, and of course a little bit up front for boot. A smooth-running IDE is however a clear improvement over a sputtering SATA - sometimes drives are out there sputtering for a while before actually failing, and that will suck your machine down. As psycoak said, a lot of it just depends on the individual drives.
I'm on an IDE root drive right now after being on SATA and it doesn't bother me a bit. Now I have to tell you I don't stare at performance numbers, seriously that stuff can make a person crazier, I just want things to work well without throwing piles of cash at them.