For all those who still want a Silhouette SD let me share the good news. Silhouette has dropped their prices on their site to $249 since announcing the Cameo. They are selling out their stock of the Silhouette SD. Prices may drop again before the Cameo is released, depending on how sales go now. You can find discounts codes to get the machine for $175 right now at these links: Infarrantly Creative, Today's Creative Blog. Just copy their coupon codes and use it on Silhouette's online store. The codes are also good for 20% the materials and their NEW starter kits - so if you already own the machine and just need to buy some supplies, go get that code first! Check out the great blogs while you are visiting too.
I also found it discounted HERE for $174.99 but shipping is free! I haven't ever purchased from this site though, so I can't give you a well informed recommendation. If you see any other deals, feel free to comment and let other readers know here.
Don't forget, I did say they are most likely to drop prices again. I purchased my Silhouette just before the new Silhouette SD came out for $120 because it was the discounted model. It wasn't as popular a machine then, in fact, I'd never heard of it, but with it's massive growth, I'm certain there will also be a lot of used machines being sold once the Cameo is available as well.