Here’s what I did: I created a standard cube, put SubSurf on with Subdiv 2. Than I rotated the view like in this Image.
In z-buffer mode with Limit Selection to Visible on I tried to select the left face of the cube. Trying to select the face directly didn’t work, I had to select right from it. It looks like selection takes place using the Optimal setting for SubSurfs. Also When switching to edge selection the back-edges on the cube can still be selected.
Is it a Bug or a Feature? Let me know
You can only edit the low-res cage of the subsurf object. That’s how subsurfaces work. That is why it selects the low-res cage when you try selecting a face from the high-res output mesh. You can’t edit the output mesh because Blender (or any other package that I know of) can’t edit the low-res cage acording to your modifications in the high-res output mesh. If you want to edit the high-res output mesh you have to free it from the low-res cage but I’m not sure how it’s done in Blender. Perhaps you disable subsurf and then tesselate the low-res cage? 
Never used subsurfs in Blender.
alt+c will create a new mesh object with the subsurf applied to it
the vertex groups will not be correct [last I checked] but it works okay
some applications, [zbrush comes to mind, probably maya too] do allow you to edit subsurf cages at different levels of subdivision [with maya letting you mess with the topology there… it seems weird to me but I’ve never used it. zbrush lets you deform the mesh and modifies the low rez cage accordingly [but the low rez cage doesn’t have as much detail as the high rez]]. Uhh, if you want to edit more high level in blender use the optimal subsurf draw view.
Thank’s for the answers, but that’s not what I ment. I know perfectly well how to use subsurfs. What I tried to explain is that selection of a face of the lowres cage doesn’t alway give the right result. (that’s what I tried to explain in my first message, try it and you will see). I wanted to know if others experience the same problems.
So, is it a bug, is it a feature, or is it the OpenGL Driver??
This one I can duplicate and it does look like it is using thie optimal settings for selection (Box select selects the rightmost side as well). I would consider this a bug.
GreyBeard
I think I misunderstood SoftWorks picture :-? I thought he meant he meant he wanted to select the face in the high-res mesh.
Forgot about Zbrush. I don’t think Maya has this though.
I believe Maya does
RMB will only select a face in the cage if your cursor actually touches the subsurf, and the selected face corresponds to its facet in the subsurf.
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It’s a little disturbing when you work with really distorted mesh…
I have posted this topic to the bugtracker and got a response. Apparently this is the way it should be, so its not a bug but a feature.