Really depends on what you mean with webapp... if you say hostgator I suppose you are talking about a PHP website. It's been a long time since I last used one of those services, I now host everything on my Rackspace VPS. For ~15$ each month I have a VPS all for me wich I can manage as I want.
Otherway I heard a lot of people saying that Heroku (Ruby, Node.js, Clojure, Java, Python, and Scala)is very good. Or Google App Engine (Java, Python, Go)
We're hosting matchist (http://matchist.com) right now with PHP Fog and it's great if you want to just get going. I didn't want to (at least for now) deal with any sysadmin stuff.
We threw up our custom CodeIgniter install, configured our custom domains, SSL certs, etc. and there was (and still is) very little friction in getting going. Their support is also fantastic - immediate instant chat every time.
That said, if you're looking for granular custom control, PHP Fog isn't for you. (No cron jobs, no access to logs, etc.)
