That is exactly what Stack Overflow uses: keepalived to manage a virtual IP between two decent sized baremetal HAProxy servers (w/ bonded 10G nics). Works great and combined with DNS or Anycast based load balancing can scale pretty damn well. Definitely worth investigating as a KISS approach. To quote a recent Atwood tweet:
"if I have learned anything in my career, it is the shocking effectiveness of building ... literally the stupidest thing that could work. (And then iterating on it for a decade.)"
Indeed! It powers all of the internal loadbalancing (non-direct customer facing) for ticketmaster.com. I was on the core systems team ~12 or so years ago and learned all about how great it is.
"if I have learned anything in my career, it is the shocking effectiveness of building ... literally the stupidest thing that could work. (And then iterating on it for a decade.)"
https://twitter.com/codinghorror/status/1026332543153389569