The first of any new generation isn't going to be worth the wait, or the price. Look at all the people who bought the A64 3200+ for $450 when it was released... now it's $270 just a few months later.
I think Intel NEEDS to adopt SOI if they want to get their heat dissipation down. Look how much success AMD is having with it, and this is just the first batch of processor's we've seen. They could very well make more improvements to the manufacturing process and it wouldn't take much to adopt Strained Silicon like Intel decided to go with... before you know it, you could have a 3.0 Ghz, .09nm, 1.0 volt Athlon-64 in your hands.
I don't think the Prescott will be all that impressive right off the bat because there really isn't any huge architectural changes it seems. It seems like most of the speed increases of the first retail products will be due to optimizations in HT and SSE3. I think when they switch to the new socket, then you'll see some significant architectural changes, possibly even MORE on die cache, and maybe even 64-bit capabilities.
The Athlon-64 wasn't as impressive right off the bat either because there wasn't, and still isn't any mainstream 64-bit support for it. When we finally get Windows XP 64-bit and a bunch of software properly ported, then you'll see it shine. Just like the P4 shines when you run HT and SSE2 optimized applications.
So... is the Prescott worth waiting for? Definately... all new hardware is worth waiting for. Is it worth buying the day you see it for sale on newegg? Maybe, maybe not, depending on the price of it vs. a P4C. Like everything else, a new product will have some rough edges, and the 2nd revision is usually significantly better than the first one. For example, Willamette and Northwood, Palomino and Thoroughbred, socket 940 and socket 939.