In PostgreSQL 9.0 High Performance it is not recommended to use SSD due to the fact that they write cache is always present in one form or another, and practically guaranteed data integrity during a sudden power outage. Data is written to the SSD large blocks greater than the block size of the file system, so the controller needs to cache written data in any way. And no SSD manufacturer does not guarantee that the data will be written entirely after you perform a fsync or when you disable caching. SSD can ignore all such attempts.
As file system it is recommended XFS. It is written that it is almost the same as ext3 in writeback mode in terms of reliability, but a bit faster (there are benchmark results of the author).
In General, I recommend reading, there are a lot of valuable information and the choice of drives and RAID, what pitfalls there are in each case.