Although the notion of Solid State Drive (SSD) exists for a long time, industries have made significant progress last few years.
It has become more accessible, less expensive and offering very interesting efficiencies.
Comparing to conventional Hard Disk Drive (HDD), read/write performances can be increased by ten and sometimes even more.
Because it is a very different technology, there is advantages and disadvantages.
From my point of view, the greatest advantages are the performances, the silent operations, and lower power consumption, and the worst disadvantages are performance loss in function to available free space, lower lifetimes, and finally the prices of GB (SSD with lots of capacity are very very expensives).
The performance degradation is a very delicate point.
There is some articles (like this one for OCZ, and this one of Corsair) giving lots of tuning instructions but it is still a too young "science" and there is still lots of misunderstanding.
It seems, some instructions are not really recommended for operating system (like Windows Seven), although it may be needed to improve SSD lifetimes. It is why it is a delicate subject.