I've been drooling over the idea of a sleek ultrabook with an ssd/hdd combo drive in it. First I heard of this idea was last year, right before the last Macbook Pro refresf, when the rumor sites were reporting (falsely) the new Macs would have a small flash drive for the OS files and swap along with the larger hard drive.
Seriously, you get the benefits of lots of cheap storage (hdd) with the benefits of super quick boot and virtual memory. All you'd have to do is partition so all the system files and the page/swap file rests on a little 10GB piece of flash, while all your user files, photos, movies, music, etc. can rest on the hard drive.
Don't know why more manufacturers haven't done this already by sticking hdd's and small ssd's in full-size laptops.