(This is my answer to someone who was concerned about durability, size and speed, when thinking about switching to an SSD.)
Durability: pretty much forever, based on write cycles.
I have a 2 year old Samsung Evo 840, which has been on 15 hours a day, 365 days a year.
Samsung uses a wear-leveling indicator (SMART #177) which runs from 100 down to 1, at which point the drive should be running out of go juice (although tests by others indicate that there may still be a lot of life left.) After 2 years of intense photo editing, video editing, programming and internet use, my wear leveling indicator has dropped from 100 all the way down to 98. At that rate, the drive would theoretically last another 98 years, and will be running long after I’m dead.
Being an old guy, I can rather accurately predict that reality doesn’t work that way, but my point is that I’m a heavier-than-usual user; my drive has 11,509 hours on it, and it’s still rated as having 98% of it’s life left. Other tests indicate that drive life on SSD simply is not an issue.
As to capacity, my Evo is 1TB. It is my boot drive. (Actually, I have a number of SSDs, one of which is my boot drive.) I have over 4 million files on that drive. I moved my iTunes folder (500 GB) to a different drive, as I did my Apple Audio files (35 GB) and my Virtual Machines (ie Parallels) 116 GB. When needed, a symlink replaced them on the boot drive.
It’s pretty easy to find the files/folders eating up your drive space (DaisyDisk is much faster than GrandPerspective). Moving them to a different drive is generally very simple.
While some folks have succeeded in living with a moved /Users home folder, I tried it and do not recommend it at all. It works fine for a while, but if/when it goes bad, you’re in a world of hurt.
Speed: SATA busses are rated at 1.5, 3.0 and 6.0 Gb/s. If your machine has a 1.5 or 3.0, you won’t see spectacular speed improvements (because the bus speed is the limiting factor), but if yours has a SATA III/6 Gbs bus, I’d wager you will be mightily impressed (because the spinning drive is the limiting factor.)
So, if you’re not opposed to an external drive (I won’t mention how many I have, so as to not scare you), switching to an SSD ought to be pretty much all plus.