OP, clipless is great. You will love it.
Part of the reason your legs hurt in other areas is because the pedals hold your foot in one spot and make you use one part of your muscle. With platforms, you can move your foot slightly forward or backward when part of the muscle gets tired. Also, when I switch between platforms and clipless, I need to adjust the seat height a bit. Make sure you have the cleat in the right spot too. When I first started with clipless, the LBS put the cleat WAY too far forward. It gave me toe/foot cramps and I lost some power. I rode like that for a year before I found out I could move the cleat back. Moved it back 1/2" and it made all the difference in the world.