I'm a bit late to the table, but I just wanted to consent to the consensus
TLDR: All drives fail, redundancy is key, SSDs cost more, especially when weighted for longevity.
I've had wonderful experience with my Crucial C300 64GB, which I've been using as an Ubuntu drive with nearly 5,000 hours uptime. I also keep a game or two on it, and frequently swap 20GB+ of game data when my play habits change (ie, I've done what amounts to many full writes). Anecdotally, this drive has performed admirably!
All that said, I keep all of my data on a HDD RAID (yay mdadm, yay GNU/Linux). Keeping data you care about on a single drive is a recipe for disaster at least once in your lifetime. If you have proper backups in place, dependability of a drive should not even factor into your considerations except:
1) A drive which fails faster costs more per operational hour. (Think cost per GB-hour rather than just per GB)
2) A drive failure can cause frustration, especially if the error occurs at a bad time and without a fast work-around. If you have a planned work-around (an alternative boot disk?), this is hardly an issue.
3) A drive failure costs user time to replace a drive and prepare its successor. The cost of this time depends on your circumstances.
IMO, if you have a good contingency plan, it all comes down to hardware cost vs gains. Some simulations I used to run were so dependent on large 100+GB database IO, and SSDs were worth their weight in gold (2 hours vs 2 days for some operations). If you are a hardcore gamer, perhaps load times are worth giving up a few FPS on some other piece of hardware. If you are just interested in your OS boot times or noise, obviously it depends on how much money you are willing to spend on a 'wow' factor, which probably has to do with your disposable income (or lack of financial planning).
I don't care if it's your computer-illiterate grandmother's computer. If she has any data that she cares about (server-deleted POP email, photos, etc) you should set her up with some sort of multiple-disk setup. SSD, HDD, they will all break at some point, and unless the user has a much shorter life expectancy than the hardware (<1 year?), data loss is a heart-breaking risk.