It is, however, a fascinating country and you just need to keep your wits about you, avoid the ripoffs, stay on the bike and everything will go smoothly. The best part of Vietnam is the small towns. Stopping for lunch in these places, where no other tourists go, is where you'll find a Vietnamese hospitality and sense of fun that is the equal of anywhere I've travelled in Southest Asia. Also, despite their tourist Mecca status, both Hue and HoiAn are pleasant places to spend a few days. Easy cycling from one main centre to the next.
Vietnamese food is terrific and is available every few kilometres along the road.
Lots of local buses if you need to hop one.