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.)
I like linode - $20 a month you get your own machine, service is great, docs are too. All I can say is maybe its too much for what you want. You also probably need to know what you're doing but as said the docs are really good so I think even total newbies would have no problems with copy/paste.
I've had a good experience with Godaddy, there was a lot of bad press a few months ago, but I've had no serious problems in 4 years. I have 5 or 6 different sites hosted with them.
