[hitotsz]

Originally Posted by KyleGoetz

Yes, it is. A good rule of thumb that will be accurate almost every time (there may be a few examples I can't think of offhand) is: (1) えい＝ええ、おう＝おお; unless (2) the え and い (or お／う) are conceptually "divided."

For example, imagine one kanji that ends with お and the next begins with う. This is the conceptual division I'm speaking of. In that case, it's pronounced おう, not おお. For example, in お歌, the お is the honorific prefix, and 歌 is a separate noun, so they are conceptually distinct things. Thus, they are pronounced おうた and not おおた.

Further, to quote Japanese Wikipedia:

Arigatou gozaimasu.