Sometimes I can work for hours without any problems editing pages, components and classes and viewing logs and objects and executing soql queries in the developer console.
However for some reason I sometimes end up in problems saving classes. And once it has started it usually continues making it very difficult to stay in the developer console. As it is now when this starts I have to code classes in Eclipse Force.com IDE and check logs and edit pages and componentes in the developer console.
Whats happens is that I get an error response from the server (500) and can't save the code. I will either have to wait for 5 minutes or sometimes it helps to switch browser. Sometimes I have seen this error when entering salesforce.com.
"The changes you requested require http://salesforce.com to temporarily lock your organization's administration setup"
The classes can be rather large; 1500+ rows. But once it started I get problems with small classes as well.
Please make it as good to develop classes in the developer console (without these disturbing interruptions) as it is developing pages and components and together with a few other ideas this tool will be my number one choice.