Seems they are indeed having some issues... their status page is updated now:
HTTP Routing Issue
ISSUE: We're experiencing a widespread outage affecting our HTTP routing, principally affecting apps on our Aspen and Bamboo stacks. It is also affecting API calls and the heroku.com web site.
We are currently investigating this issue further.
HTTP Routing Issue ISSUE: We're experiencing a widespread outage affecting our HTTP routing, principally affecting apps on our Aspen and Bamboo stacks. It is also affecting API calls and the heroku.com web site. We are currently investigating this issue further.