I don't know, I'm a big fan of the mfx units, have had a GT 8 for a year and would go as far as saying I would not be afraid to run my guitar through a computer mfx package like Guitar Rig 2 for a gig either.
I find with the GT, there are options available that make gigging very viable. Example would be if you find the gig has a different audio vibe that isn't working, you change a couple of parameters globally and it will apply to all your presets. The manual option really helps too. Instead of the foot switches changing banks or preset patches, throw it in manual and the switches act like individual stomps, plus you have rotary control over effects parameters too.
The downside is pouring over a pretty thick manual and hours of experimentation untill you've got a handle on things. This would be a pretty big turnoff for some I could imagine but it great fun for a self proclaimed geek like myself.