Yes, it's just webapps, Chrome extensions and Chrome Apps from the Web store. If you feel strongly that you need to install other software then the Pixel is probably not a product for you... Just keep in mind that it's pretty much the same for all tablet users, since they can also only use webapps and install apps from their vendor's store.
I honestly think the high price tag is the point. Google is trying to establish itself as a major brand that isn't just offering alternatives to Apple hardware for a lower price. Think of the plans to build retail stores, and how the Android brand is given less prominence these days: they are working hard to build a consumer "Google" brand that's as strong as Apple.
So far most of the devices they sold were priced to be cheaper than Apple's counterparts. This pricing move is trying to say "we have better technology than Apple and it's worth the price", possibly in anticipation of other high-end products such as Glass.
I have no idea if it will pay off, but it's a bold move.