[Peroni]

Sleepio appear to be doing pretty well despite a fairly average Show HN - https://news.ycombinator.com/item?id=4504639

Pixelapse did reasonably well and ended up being acquired by Dropbox (not necessarily suggesting that's a success) - https://news.ycombinator.com/item?id=3572755

My personal favourite is Mondo (or Monzo as they are now called). Their founder/CEO posted here when they launched and the thread got very little attention. These days they are one of the most respected startups in London and are on the cusp of enormous success - https://news.ycombinator.com/item?id=9638345