Not really. Maildir does away with a host of problems ranging from file locking (the entire mbox file must be locked during writes, where maildir only requires

Not really. Maildir does away with a host of problems ranging from file locking (the entire mbox file must be locked during writes, where maildir only requires the message being operated on the be locked), to network compatibility (no transporting a 4gb file back and forth), to corruption issues (mostly due to file size).