I think the pop3 checker is a great thing.  Since one can check different pop3 account at the same time it's great. But it would be nice if  one could have an option to choose what pop3 accounts to check. Now, one can only enable for checking for all accounts at once or no accounts.

 

It's supposed to be a permanent thing, i mean, you set the accounts and you don't have to change it. Why would you want to enable or disable one account from being checked? Anyway you can delete it, and it won't be checked. However if you want a quick switch, just change the server name or the port number (you can, for example, add a "x" in front of the server name). If plus can't connect to that server at that port (that's what will happen), it'll just ignore it.