Can someone here confirm that downloading electrum from the official electrum website now with the windows installer is fine?
Yes, I've done it and it is fine. As long as you make sure it is the official website and not a phishing one. Verify the signature to be extra safe and protect yourself from the extremely unlikely event that the site has been hacked.
Anyone here still using the old electrum and opened it and have no issues at all even though it was recommended by theymos to not do it?
I had Electrum open when I first saw theymos message. All my BTC are safe. The vulnerability was reported to Electrum rather than being discovered by someone exploiting it. The exploit would be via a website running javascript so you would have to not only open the old Electrum but also visit a malicious website (which there is no evidence even exists) at the same time.
The other thing is what percentage of electrum users even know about this? Because even if you use electrum a bit, the only way to know about this would be either visiting this forum or going to their website. And obviously someone isn't going to check electrum website everyday to check for the new update etc.
It would be a reasonable suggestion for Electrum to add an automatic notification when a new version is available.
In general, just calm down and upgrade. If you are holding a large amount of BTC then it shouldn't be on an internet connected device in the first place. Get a hardware wallet or use an air gapped cold wallet.