I got my F1 and finally got to have a quick audition last night.
I would start by saying that I prefer headphones, because I can never get good seal with almost any IEM. Maybe my canals are of weird size and shape, but whatever the reason is - headphones just work!
Having said that, the F1 with default silicon tips on, gave me a decent seal and was comfortable (used it for 1 hour, no fatigue or discomfort).
Personally, I never use inline controls, so would have preferred a plain cable. Not a problem, just saying.
Now, what about the sound? Well, out of the box (i.e. no burn-in) they sound amazing for $1.99
Is it worth $15 (normal price)? YES!
The F1 is not neutral, which for me is a good thing (I like a little bit extra bass). Purists would complain about too much bass, and bass heads would not have enough, but everyone else would just enjoy them for what they are!
Also, not a big surprise - the F1 is not very detailed. For list price of $15 - you'd be naive to expect anything more...
I have not tried any amp, and I seriously doubt an amp would improve on those.
My F1s are going to live from now on in my work computer bag, and be used for conference calls (got MANY of those every week) and for light music listening at work (out of my iPhone 6S and macbook laptop) to block off my noisy and chatty neighbors from across the aisle