What free mail client with Google calender support to use?

[Hybrid Vigor]

I'm currently using Thunderbird with the Lightning add-on, but not that the whole thing is just sluggish, it's error-prone as well. Syncing IMAP takes ages, too.

Is there anything comparable which has support for Google calendar sync in one program without any hassle of registration or hacking to make it work?

Google doesn't really help me out.
Thx for commenting.