We went out this afternoon to buy a base Prius Two and came home with a Prius Plug-In. It turns out that the Prius Plug-In was a better deal. $4000 Toyota incentive plus $4000 in tax incentives brought the net cost down to about $21,900 while the Prius Two would have been about $21,600 with the optional non-optional equipment like floor mats. The Plug-In has the navigation system, the back-up camera, HD Radio and a bunch of other features that were not really important to us like heated seats and digital ashtrays. Plus of course the HOV sticker (if we can get one before they run out of the 15,000 that California jut released). Also, this is one of the rare times when Northern California Toyota dealers had better incentives than Southern California dealers ($4000 versus $3000)--usually it pays to drive down to Southern California to buy a new Toyota.
Downside to the Plug-In is the lack of a spare tire (the batteries take up all that space). You get a compressor and some tire sealant. You can buy a wheel and tire but then it would take up cargo space).
These are in short supply due to the incentives expiring soon (7/7) plus the rush to get one of the new supply of California HOV stickers. The one dealer that was going $600 under invoice was sold out. Most of the dealers were about $600 over invoice. The dealer we went to was at invoice (that was the Costco "deal"). We would have paid cash but they had 0% 60 month financing. If we factor in the interest we'll get on the money we didn't spend in cash that brings the Plug-In to a bit less than the Prius Two.
I drove it home while the spousal unit drove home our Camry Hybrid. The difference is really noticeable in terms of power and quietness. The Camry Hybrid has much better acceleration due to the much larger engine, and is very quiet. The Prius Plug-In has a lot more road noise and unless you push the button for higher power it's anemic in accelerating onto the freeway.