Solid state hard drives are becoming more and more popular. However, they are still considerably more expensive then more traditional mechanical hard drives. Recently they have been dropping in price but they still have a long way to go until they are as inexpensive as mechanical hard drives.
Putting the cost factor aside, when strictly comparing the two, they do offer many advantages over traditional mechanical drives. They are much faster and offer great performance increases then typical drives. I have personally seen laptops advertise boot times less than 20 seconds. They also are more attractive to the laptop and tablet markets because since there are no moving parts in a solid state drive they are much more durable against the accidental drop.
With the performance and durability increase why wouldn't anyone want to go with solid state drives (of course besides the price). The answer to that question I believe can be seen in the warranties you get with them. Typically when it comes to the major manufactures traditional mechanical drives come with a 3 or 5 year warranty. With the solid state drives it's usually more like 1 year. This tells me they aren't reliable and wear out more quickly than traditional drives. With solid state drives becoming more popular you do see more reviews coming back stating the drive died in 2 or less years. This poses a great problem to people that don't run regular backups to another drive. While we are there lets me honest most of us aren't as good as we should be.
So how should we use this great new technology? Personally I feel one should have a solid state drive as their boot drive with whatever OS loaded to it. I also recommend installing frequently used programs to the solid state drive, while keeping all your data like music pictures and movies stored on a traditional drive. Most desktop computers will be able to accommodate the addition of a solid state drive; however, I feel most laptops will not. I have only seen a few instances where a laptop will support dual hard drives and those laptops are usually higher end laptops that most of us don't have. So if your laptop only supports one hard drive I suggest you stick with the regular mechanical hard drive. At least until the technology is developed more and they become more reliable.