New Asynchronous Adsense Ads and why you need them!

You may or may not have noticed, and I'm betting many of you won't have, that when you click on 'get code' in your adsense ads you will now see a box just above the code that defaults to 'synchronous' however if you click on the 'synchronous' wording it pulls up a drop down box and you can select 'asynchronous (beta)'.
If you don't know what effect this has and why you really want to select 'asynchronous (beta)' then be aware that if your ads are placed at the top of your page then if the normal 'synchronous' option is selected then the rest of the page doesn't start to load until the ad has. This often causes large delays and slows down wordpress considerably.
If you select the asynchronous option the rest of the page continues to open and isn't held up waiting for the adsense code to download.
I came across this last night, whilst trying to speed up a site that was taking over 3 secs to get a 'first view', after switchign the ad format, the 'first view' time dropped to 0.8 secs. That to me is worth having particularly now that google are including website download times in there ranking of your website.
All you need to do to make the switch is to select 'get code' on your old ad, change the drop down box to 'asynchronous (beta)' and then copy and paste the new code into your website to replace your old ads. All colours and other settings remain unchanged, it only affects the way that the ad is delivered.
Hope this helps - for me a gain of 2+ secs in first view time is worth it's weight in gold.