In Windows, I was relying on Google Talk to check my Gmail account for new emails. It was also providing easy and secure access (without entering Google master password) to my Google account.
In Linux, I am using Gmail Watcher plug-in for Firefox.
Contra: You need a running Firefox to see it, which is a disadvantage in comparison to Google Talk. You also cannot benefit form Google application passwords if you use two-step authentication.
Pro: Unlike Google Talk, if a Gmail tab is already open, Gmail Watcher doesn’t create a new one but switches to the one available.