I have posted this elsewhere, but forgive me I believe this falls under 2 categories, both a 4.0 issue, and a general feature request.
The 3.5 way of making a circle could be described as a diameter method i believe, this is ok, and it allows for making concentric circles (a very common thing for circles to be) quite easy with the help of the shift key to keep the circle in perspective. This is also the way the circle select toll works even in 4.0 Beta
The 4.0 Beta way of making circles has the first click by in the corner of the circle, not generally as useful a location and moreover terribly hard to make concentric circles, really is is very hard and next to impossible and requires working on different layers and watching pixel numbers and re-positioning and so on, and if you want the gap between the circles to be small it is really hard to get this method to work without lots of trial and error redo's that take time.
The IMHO BEST was would be for the click down to mark the center point of the circle and then as you drag the pointer one you describe the radius with the pointer.
While I would love the latter, I could be very happy with returning of the 3.5 method, or the option to choose between all 3 would be pretty cool if anyone actually cares about the other methods.
But the beta way ain't the better way.