The Crossgen complaints sound incredibly greedy. Even when games were not cross gen last generation, they still ended up gimped because converting the height of gaming on "sub HD" to the world of HD took devs a lot of time. So we started with a load of RPGs with lacking towns, or games that reused / stretched assets much more than the previous games in the same series.
Now, Cross gen might limit some of the pure current-gen potential, but hopefully we'll get much fuller, equal to last-gen sized experience out of it. Then, in a few years, we get the dedicated-to-latest-gen experiences. Along with all this, people who can't afford a $400 / $500 system, but still can afford a $60 game or 2, can enjoy the latest game in a series they love.
The only real problem I have with this... is that I wish they'd figure out some solutions to either enable cross-generation play, or offer more cross-buy incentives. The systems are not competitors, they're sister systems. Offering a free digital copy of the XB1 version for those who get the 360 one, and ability to transfer save via cloud, would be a nice gesture. And it'd sweeten the deal for Previous Gen people to more easily switch over to the newest gen sooner, rather than later.
I never got into Horizon 1, but it's demo charmed me. I like the less Sim, more Outrun-feel of the game. I can see myself getting into this game a lot sooner on XB1 than on the crowded library of 360.