It can be faster for loading files that you load all the time. If there will be multiple files accessed all the time then it will always be loading files into the SSD cashe and then get purged from there once they aren't the most used. using it as a boot drive is good as most of the time core window files get put on the SSD part since they are accessed all the time.
I have a 750GB SSHD in my laptop and honestly I never saw much of a different between that and my 250GB WD Black was orginally came with it. I found that using the right defrag program to properly defrag your hard drive is more effecient than a SSHD. But by all means buy one. Won't hurt anything. just I don't think the Hype on them is as good as it really is.