Its a worthwhile investment if you have a lot of USB 3.0 devices, since you (and nobody) has devices at this point, I don't see USB being a make or break decision for purchasing a MBP. Pumping > 2k into a new laptop means you may want to wait till the Arrandale chipset is in the new MBPs but USB, meh. I don't see that waiting is a good thing.
But a year after you buy the laptop, you might have a lot of USB3 devices, at which point there is no way to upgrade, if you have a laptop with USB2, without selling the laptop.
In my opinion, LightPeak won't be successful unless it is included on a significant number of computers in the first quarter of this year. I think if Apple added lightpeak ports to the soon-to-be-released MBPs, LP would have a chance of success. Otherwise, USB3 will take off and LP will go the way of Firewire, not a common option on computers and only used by some specialized devices. Intel might be trying to delay USB3 by not putting it on their chipsets until 2011, but more and more computers are going to include USB3 whether Intel offers it or not.
I want LP to win over USB3 for the next high speed peripheral interface because like Firewire, it is technically superior to USB. LP is faster and the cables and connectors can support essentially any protocol, so it could be used for all kinds of devices, even displays, and longer cable lengths are possible. Having just one kind of connector for everything would be great (if that's what Intel is going for), and I could throw out my giant collection of cables and adapters and just buy a few LP cables. Unfortunately, USB3 looks like it will be first to the market, and it has the advantage that it is backwards-compatible with the millions of USB2 devices out there. I think LP is not really ready, though, which is why Intel would have to delay USB3.
There is a fair chance that Apple would be the first manufacturer to get LP, since Intel has given Apple special treatment before, and since Apple doesn't mind using different connectors (Firewire, Displayport). Unfortunately, Apple seems to be becoming more consumer oriented, so they might stick with the normal USB and Firewire combo, possibly going to USB3 when they see fit.