If there is any compilation error, developer console does not show errors and what is more confusing is that it does not report that save was not successful. There is also no feedback on successful message other than the asterisk in tab for the unsaved files.
I have been observing some odd behaviors as well. However a big negative with the developer consoles which compelled me to move away from it for the time being until it stabilize are.
1. It Overrides the code. As compared to force.com IDE, which gives warning if page on server have been updated by some body else.
2. Save/compilation issue as you mentioned.
3. Developer console is being too heavy for the browser to handle efficiently, resulting it being slow.
4. Most of the time if debug logs are large it doesn't load them at all and gives error.
As of now I use it for following only.
1. To check the line-by-line test coverage of the classes, as there is no other alternative now.
2. RUN some quick queries and update them, then and there.
3. Anonymous execute apex.