I'm not sold on the HP4. The launch control is killer. But the electronic suspension, ehhh. You can buy some awesome Ohlins suspension and carbon fiber fairings for the same price.
It would be great to have adjustable traction control on the fly, though. But for the additional cost. I think you can build an S1000rr that will be equally as nice, if not nicer.
I think electronic suspension still has a few years left before it's perfected. Soon, they'll be introducing a new and improved model, etc.
Nonetheless, I'm going to be keeping my eye on eBay for a wrecked HP4. It won't be long until they start showing up. I'm sure. I wonder if the ECU and other components can be swapped out with the S1000rr to gain "on the fly" adjustable DTC. Knowing BMW, I'm sure nothing would be plug and play. But, where there's a will, there's a way.
But, this entire post is just being written to make me feel better that I didn't spring for the HP4. Oh well. Like I said I think the suspension will just get better over time, and I'm still not convinced it better than a $2,500 Ohlins fork. Given that stock OEM forms are selling for about $1k, it's really only a $1,500.00 investment.
In fact rebuilding the stock forks is also another route. There's a lot of room for improvement. In terms of power to weight ratio- the two bikes are so incredibly close, when they're "wet" that there's no need to do much work on the powertrain- at least to get it to the HP4 level.
My $0.02. I feel better already.... ;-/