If anything they would be an even greater boost on slower sata II computers.
The HDD is the biggest bootleneck on any computer, old, or new.
NOW that is not a recommendation to run out and buy.
It will boost turn-on time and program loads.
It will not:
(1) play movies (DVDs/Blu-ray) any better.
(2) It will not make games play faster.
(3) while photo shop program will load faster, it will not speed up editing photos unless they are on the SSD. Normally most tend to store the Photo on the HDD. Depending on individual size a 100 or so photos can take up a lote of space.
Now you know, the ball is back in your court to decide if it is worth it.
I have in two desktops and two laptops, and love them. BUT they do NOT speed up my typing, nor do they improve my spelling.