I was pretty close to getting Seagate's Momentus XT but have been scared off by the many problems reported on forums and feedback sites, especially in Mac Book Pros. So I'm waiting for mk 2 with some extra flash and better reliablilty I'm assuming will come out this year.
What would suit me better though is a 32+500 hybrid drive where I have more control over what is on the flash drive and what is on the disk drive. So there are 2 physical partitions within the one 2.5" hard drive enclosure which use different media internally (32GB for core files and 500GB for data and multimedia). The partitions would be locked so they can't be changed. - Or even better, the disk driver just makes them appear as two disks to the OS that share the same bus... Perhaps it's ok if the bios just sees the first drive until the OS is loaded. Is either of it technically possible? Obviously difficult to market outside of the enthusiast market.
The SSD memory modules can be pretty small right, so they could even make them a card that plugs into a secondary connection on the enclosure. That would be good for computer builders as well as for upgrading and recoverability. Then future operating systems could recognise these system SSD drives and automatically install the OS + swap files on it. While placing document libraries on the larger data drive. While in the longer term HDD will probably disapear there will always be a trade off between speed, storage size and expense.