I had them on stacked because I didn't realise you could change them till I saw this poll. O_o I swapped over to thumbnails - that seems much easier because if you have multiple status updates from one person you can view them all from within the notifications screen.
Tbh I didn't even know there were options. I just mass delete them generally. The only time I actually click them if the one that happens to be 'in front' is from someone I consider a buddy and seems important.