We downloaded copies from the Microsoft Connect Website for both XP and our Windows 7 RC box.
Set-up was essentially seamless.
Being a touch cautious, we offloaded Avast (on the XP3 box) and AVG (on the Windows 7 box) before installing.
The program goes through a validation check (IE: You must be using 'genuine Microsoft software') prior to installation, then in an easy step-by-step fashion, downloads current virus signatures and goes through a quick default scan of your PC.
Unlike other beta testers, Windows Essentials (previously code named 'Morro') found no spyware or viruses lurking here.
Perhaps that's because we use CCleaner on a regular basis to clean out our caches, junk files, cookies, etc ... or ... the other AntiVirus software just worked ? :)
Interestingly, there was no problem logging into Microsoft Connect using Firefox to download the new Beta.
While some other pre-release articles are noting a limit on downloads, we were unable to confirm this plus (check this out?), Microsoft is currently running ads on Google announcing the release:
Security Essentials will replace Windows Defender on your PC if you use it. So far, memory use on both boxes appears minimal.
Microsoft has stated that Windows Essentials is not an attempt to replace commercially available AntiVirus solutions but to spread a touch more security to those that can't afford more elaborate programs.
Of course, with plenty of free programs out there, most notably AVG, there could be a bit of an argument to be made there.
On the other hand, if Redmond designed the program to run better with their own software as well as proprietary pieces, it might be 'a good thing'.....
Update 1 - 2 PM ET: ZDNet is reporting that downloads will be capped at 75,000. Liveside.net is saying it 'might be changed'.
Update 2 - 10 PM ET The beta is still available at this hour (no doubt exceeding 75,000 downloads) and is also available with an interesting write-up at BetaNews here.
Update 3 - 11 PM ET An alert Digg user (with thanks to 'diskserious') noted that the disabling of Windows Defender is not yet active. The Microsoft explanation can be found here.
Final Update - 11 AM June 24 - As of this morning, downloads were no longer available in the US.