So basically I've got a Gt100 and I was wondering if any of you have any experience recording with this or other similar devices. Do you use anything else with it (amp sims, etc.)?

I was planning to use this to record songs with my band, and going into a studio only for the durms and vox, is there too much of a difference between this and a mic'd amp at the studio?

Here's something recorded with it https://soundcloud.com/nicocastro95/survival-cover
I use a Digitech BP355 to record, and it does the job perfectly fine for DI guitars and bass. I usually use a completely clean patch and use amp sims, but that's because the modelling on the BP isn't even close to recording quality, or the tone I want.
The GT has perfectly acceptable modelling though, so if you get the tone you want out of it then there's no reason not to use it. I'm a fan of trying as many possibilities as you can so I would still suggest trying some amp sims, but if the GT is the exact tone you want then it makes no sense to go chasing after the tone you already have.
I'll probably try some amp sims then, just to see how it sounds. I'll probably just stick to the GT though.