The possibilities with this effects unit are endless. The distortion settings are frankly terrible, it's equipped with flimsy plastic jacks, and there is a definite learning curve when programming it. It's also cumbersome to navigate even after you have programed presets without a midi footswitch, however this thing is worth it. They can be found for under $100 and offer some of the most lush modulation, reverb that dwells for 40 seconds, or crazy reverse sounds, and nice compression.
The yamaha FX500 is full of great reverbs, delays, chorus effects. It even has a compressor! But the overdrive and distortions are absolutely the pits (IMO). I think this was used a lot on the band SLowdive's Souvlaki Space Station. If you're a tweakster you'll love it!
I admit that I don't want to program this stuff. I just bought it because I love Slowdive's sound and guess what, they used the preset 39 and 40. So plug a strat add some reverb, then to add some reverb and at the end of the signal don't forget to add some reverb and you have the Primal sound.