Solid State Disks (or SSDs) using flash memory chips instead of a rotating plater/head assembly like traditional hard drives are great. All of my systems here have one as the primary disk. Especially in a laptop situation the extra reliability and a computer that is completely silent are very welcome, as is the speed. They are fast, really fast when reading data of the disk—Windows starts in few seconds and applications near instantly.
The problem is the write performance, and it gets worse with time. Writing data to a SSD* first involves first clearing a whole block and then writing data to it, and this block clearing is slow. To compound the issue, the filler/more used the disk the less likely there will be an already clear block. To the end user this clear/write cycle is worst with small random writes (e.g. a web browser writing to its cache, or version control software updating meta data—yes Subversion I’m looking at you!), and causes the whole machine lock-up for as much as 10 seconds at a time.