I might as well be honest and say i've had the Sigma F80 brush for about three months and have only used it a couple of times. I decided it was time to play around with it and see if it would work for me and i've been so happy with the results! I normally apply my foundation with my fingers as I bought a really cheap flat foundation brush and it just made my foundation streaky. It made me a bit reluctant to try any other brushes for my foundation but as this one is a completely different shape I can see why it works so well.
I currently use Maybelline Dream Matte Mousse foundation so I didn't think it would work as well as liquid foundation when it was applied with a brush but surprisingly it did. I'm not sure if I use more or less foundation than I do when I use my fingers but I don't mind as it gives such an even 'airbrushed' finish. It also makes applying foundation a lot faster as it is quite a big brush and this is great for me as i'm always in a rush! It's also really easy to wash even though there are a lot of bristles and it hasn't shed once which is brilliant.
It's safe to say i've been converted and like a lot of people, the Sigma F80 gets a big thumbs up from me :) You can purchase it from Sigma for $16 which is around £10.