Speed is a great advantage, if you need it.
Disadvantages are price and limited write cycles. How limited, I do not know yet. But on average, an USB flash drive will last about two years until you start to have problems.
For a desktop, I recommend Solid state for operating system and programs and traditional hard drives for data storage.
For laptop, toss up. But remember, had a solid backup plan. For $50 a year, carbonite rocks!