Ebay had the advantage of a tremendous amount of free publicity because of when it started. While it's no longer relevant whether it's a good name or not that is certainly worth mentioning.

Heroku is an interesting name and has trademark and brand potential certainly because it's a made up word. The problem is it can be confused spelling wise. You could do hiroku or hirowku or herokoo just to name a few. It's usually a good idea if possible to steer clear of names like this lest you want your email, or some web visitors to end up in the wrong place.

A great name depends on the circumstances. Things have worked for heroku obviously given who they are selling to. It might have been a good name for a car model as well. But I wouldn't say a heroku like name is the right choice in all situations.