I went from a VF16 to a Roland 2480DVD... The FX on the roland totally blow away anything my VF16 was capable of. I always used outboard modules with the Fostex.
The VF160EX fx are ok. But they pale to a decent processor. I run an old Lexicon Alex and it's quite a bit better than the fostex. I've also got a Fostex VM200 digital mixer with onboard fx and they seem a little better than the VF as well.
The one thing that sucks about fostex is that they never build in dedicated returns. You have to lose a channel or 2 for the returns.