I am building out the front-end of a CRM and I have started using a lot of SVGs for smaller elements. I can't believe how amazing it is working with illustrator and SVGs. As far as actually designing a complete UI in illustrator, personally, I couldn't do this because of lack of knowledge but I can definitely see the positives.
Yes, icons and small motifs made in Illustrator and SVG using pixel preview is ace. Looks lovely on retina too. I do that and fall back to png for devices that can't handle svg.
