Is myibidder still working as a firefox extension?
since eBay has changed it's look there is no myibidder icon anywhere.
Surely i'm not the only one noticing this.

That was discussed in the forums several times.
eBay is still rolling out their changes and we have to wait for them to complete before making an update.

Meanwhile, you can use Tools - Snipe it option in your Firefox browser.

I have already experienced the same issue. Funnily enough, on German Ebay it still works, only ebay.com has changed its layout that dramatically.

eBay usually starts making such changes on ebay.com first.