I'm fairly new here and had never heard of these sites:
Busy.org
chainBB.com
Esteem
Steepshot
Zappl
Like you mention, the value of Steem (both the cryptocurrency, blockchain, and as a social media site) will continue to grow, and I definitely believe more apps like these will be developed in the future.
Upvoted and was about to follow you, then I realized I already am! ;)