If you can find a Sandy Bridge CPU and Cougar Point (H67/P67) mainboard available, go for it. The increased performance is definitely worth the hassle of having to switch the mainboard out when fixed boards arrive in a couple of months.
I'm very happy with my SB system. If you can live with your current system for a couple months... I'd say hold out.
I expect the pricing to be comparable to pricing at launch. Intel typically introduces processors with pricing that replaces old processor price points. The existing targets haven't moved... and people say what the SB processors were priced at... so I would be very surprised if it changed.