Mine was working fine up until yesterday, when I found out there was that update (had been using the previous version quite happily). Haven't had it work quite right since then...
First, it wouldn't show any mail at all. Now, it will go back and forth between how many messages I have, and zero. It'll make it's noise when I get a new message, and I go to look, and yes, I got an email, but no, Gmail notifier still shows 0 email messages.
From there, it will make the 'new mail' sound every 5 minutes or so for the next two hours, when it will spontaneously stop making the noise, and for about an hour (or less), you can actually see how many new messages you have. And then it stops, and we go through the whole routine again. It's all rather fun.
Er, um, no. It's not. I had gotten pretty used to *not* opening up Safari to see if I had mail, and more importantly, seeing if it was mail worth reading...