I have it and because of it have phased out sai and photoshop (I used to work with all 3 when working on MS4, now I can pretty much do everything I needed 3 programs for before in CSP/MS5) It works best for what I need it for, my only issue is that editing/warping the sound effects are not as easy for me to do in MS than they were in photoshop, but for the difference in price (especially this price) it's a small thing to deal with.
As for EX being worth the extra money or not, yeah, it's worth it if you intend to use those features (I know I do and they are very handy) They're not necessary for all artists (everyone works differently, so there are many that never make use of those extra features) As and artist you'll know better than anyone else if your style and methods require those extra features or not.