In general, the Greek smaller and rural routes were on very good, smooth roads without much traffic. We found that there were many routes with a small road running parallel to a main one. Unfortunately, there is often no option but one very busy main road into some of the cities. Thessaloniki, Larissa and Athens were the worst, with multi lane traffic unavoidable.
Stray dogs were a bit of a problem, but we never had any serious run ins.
Campsites get extremely busy in the high season and we found some to have no space available when we turned up (August.) This was a particular problem on the coastal route to the North of Larissa.
Blog post for Greece: