I guess it really depends on how much you are going to use it and what you are going to use it for. for me it was worth it because i do alot of posters for local places. i also use it to edit photos , make website layouts and normal sigs/splashes so mine gets used alot.
You could always just use to Trail version of Photoshop till you get use to it then think is it really worth getting the full version. if not there is always gimp and another one whats abit like gimp but i cant remember the name of it at the moment , i will post back in here if i find it though . i havent used gimp or this other thing though so i cant tell you what they are like , there is even Paintshop and Fireworks too you could have a look at.