Yah, opening photoshop and also opening large documents in photoshop and saving. the rest comes down to the cpu and ram. The main things people want ssd for is to put their apps and the os on but keep all their movies music pics etc on a huge 1/2TB 7200rpm drive. Just drag the document you want to work on to the ssd (if the document is huge) before working on it then drag it back once you are done.
If you use the SSD as scratch drive for Photoshop, it should be noticeably faster. Aside from that, opening the app and documents should also be faster if they are on the SSD