I was looking for a preamp that would give my guitar and vocals a transparent sound as well as add some color when I needed it. ISA one does that. I have a basement project studio and no one else but me uses it but me (maybe a friend or two). My point is I'm not in the Music business and I just want to record my stuff. When I cut my teeth in recording I worked in real recording studio with lots of excellent mics, analog outboard gear and 2' tape. This was back when digital was thought as noise reduction not the beginning the middle and end of the process. Back to the review, I can't afford to buy the gear my ears are use to for that matter who can? This Focusrite ISA One is great analog to the gear I was able listen to back in the day and at a price I can afford. That said the ability to have separate outputs for the DI and mic/line make this preamp a twofer. Well worth the price. Quality in and quality out the ISA is just that.
As a professional voice over artist I was looking for something a little extra to make my recordings sound even better. I already use a focusrite scarlett 2i2, but thought this might give it a little something more. I read reviews and they were mixed. But, I bought one anyone. It makes only a minimal amount of difference. It's so minimal that it's not even truly worth mentioning. Maybe if you don't have a good audio interface, or a great sounding mic it will help. However, if you've already got good equipment - this probably won't do much for you.