I've used Izotope and it's cool. Easy enough to use when you understand it and it's kinda what everyone uses.
But is it really necessary ? no, absolutely not. It obviously is a fancy software. It does the job well, i agree, but there's freeware doing the same thing.
I use Flux STTools for Stereo imaging, ModernExciter for Lows and High, Fruity Limiter for compression, Parametric EQ 2 for EQing (of course) and Maximus.
Flux STTools is Free, ModernExciter is Free. Fruity stocks are includes in FL Producer Edition. They do the job on the same level than Izotope.