I find that expensive still for mechanical drive and SSHD is only 8 MB SSD, the 64 MB cache that's deceiving.
IMHO there's no real downside to owning an SSD. Ultra quiet, low power, not nearly as shock sensitive as a mechanical drive. Less weight too. That's important in laptops and other mobile devices. As with any system, making regular backups will keep you in a good place. EDIT: DRAM SSD's ?!? Who would make and sell something like that? @whizkidraj: You can safely delete that link from your bookmarks.
I have a Samsung 830 series (512 gb) and it works great for me (I hope I don't jinx it...) In the case of a laptop, You only need to check that the SSD fits in the existing drive caddy. Make sure it doesn't protrude above the top any more than the original drive does. Otherwise, it won't fit in the laptop. Regardless of whatever SATA port (3 gb / 6 gb) this drive is on, you should still see a substantial increase in performance with the drive. Of course, that depends on the speed of your CPU. OH, and someone told me that DRAM based SSDs are often used for servers to provide caching. (To increase performance) I stand corrected.
Thinner SSDs (all of the new ones) are universally compatible with the older caddies as the side of the drive with the screw holes and interface is unchanged. The only issue is that if there is dampening material that is supposed to make contact with the top of the drive, it wont. Since SSDs are non-mechanical this is not an issue as they are not vibrating nor susceptible to typical laptop vibrations.
Those 850 EVO's are getting hard to find because Samsung has come out with the 860EVO to replace that aging 850. They are supposed to be a little faster and have a better warranty than the 850's too. The 860's are a few dollars cheaper than the 850's on Newegg. I just got two 860-250gb (because they were on sale) yesterday.
As the stock of 850s depletes this trend will continue. I just picked up my first 860 EVO and 860 Pro. While benchmarks are better you can't "feel" the difference. The main benefit (to us) is better warranty endurance and (to Samsung) they are cheaper to produce.