In addition to optimization, your system can by tuned and upgraded to increase performance.
RAM; at minimum, 2Gb of RAM are required for modern systems. 4 is better, you can’t have enough for Photoshop, so max it out. I can install RAM in any Mac. I will only install a few brands of ram, Crucial and Techworks. Cheap RAM is nothing but problems and you could end up spending a few hundred dollars figuring out what is going on.
New Hard Drive; drives get slower as they get older and you may not have had a fast drive to start with. Laptops may not see much benefit from a faster drive, but certainly will from a newer one if they are two years or more old. iMacs and Mac Pros will always benefit from a faster drive and Photoshop will always benefit from an extra drive. Solid-State-Drives (SSD) are the new hot thing and are a blazing fast solution… if you get the right one. If your drive is over 90% full, performance plummets (and data damag inevitably occurs). You will see a lot of benefit getting a bigger drive, especially before those important files start to refuse to open .