Due to the price years ago, I have been a user of PSP as one I could afford back then but now want to make my first purchase of Photoshop after seeing how much it can do that PSP cant. I see all the marketplace items talking about stlyes and scripts or actions etc., and the availability to do so much more now is too big to hold back any longer. I have no idea of the growth of Photoshop other than reading about Photoshop7 then CS3 and now googling for prices I see CS4.  
My question is- is this the latest version out and the one to purchase if I am going to take the plunge?   I also figure I might as well get the latest because I may not be upgrading too often so any suggestions will be greatly appreciated.

Thanks
Pat