I must say, I'm fairly excited about the prospect of a server running solid state disks.  You may recall my exuberance about the prospect of the solid state laptop.  If you query google, you will find a wealth of good stuff on the subject including a case study involving the massive multiplayer online role playing game called Eve Online.  In the case study, it says:   

"CCP Games has a multi-tiered architecture with front-end web and proxy servers connecting to the EVE application servers and back-end database servers. The database servers are running SQL Server 2000 and are clustered using Windows 2003 Server Enterprise Edition. Setting up the 64-Gigabyte solid state disk was smooth and simple. From a DBA perspective, the solid state disk presented as just another storage device so there was no learning curve, despite this being CCP's first experience with solid state disk. CCP moved the most heavily accessed data onto the solid state disk, along with the "tempdb" and the transaction log file. One table alone gets 8 million records added per day plus a huge amount of selects and updates. Less frequently accessed data remains on conventional IBM storage.

The Result: 4000% performance improvement"

8 million records added per day.  We take our online gaming for granted don't we.  Anyhoo, the future for data storage looks bright indeed and solid state disks will certainly help alleviate many an I/O performance problem out there.    Of course, if you want one now, you'll have to add it in.  I don't think any of the major server manufacturers are bundling solid state disks yet.   I don't know why the hell not, if they're available!  (maybe they have a more lucrative arrangement with the traditional hard drive manufacturers?).  I would certainly think hard about paying the extra money to upgrade when purchasing a server if I had an application that did a lot of heavy lifting on the SQL side.