Here's a link to a post I made months ago about my retrofitted susans in a corner wall cabinet. I have total access to everything in every shelf. The most efficient use of storage in my kitchen!

http://ths.gardenweb.com/discussions/2682846/update-on-susans-in-corner-wall-cabs-from-a-tko-to-others

I really cannot see how the lower shelves could obscure the upper. I can reach everything on all three of the lower shelves without standing on a stool. And I am only 5' 2" tall. The top shelf is mostly dead storage. It is great that I can adjust the susans verticalyl if needed. Difficult in the narrow spacing, but possible! Very little waste space, either vertical or horizontal. Notice how little space is needed above items when you can rotate everything to the front for access. (I think it is interesting to compare my current use of this space as shown in the above post with my original use in the post below.)

Do be sure your susans are sized to maximize the usable space. Below is another old post that discusses this:

http://ths.gardenweb.com/discussions/2692033/retrofitting-supersusans-in-upper-cabs-a-long-success-story?n=28

Look especially at the 4th image from the top that clearly shows how little waste space is left on the shelf IF the susans are correctly sized for your shelves.

Thank you Bellsmom for this info! I found your linked post earlier this morning. They were among the few threads that deal with upper SS. Regrettably my Susan's are fully round so I lose some space. Bummer. I appreciate you telling me your height. I am 5'4" if I stand tall.

Yeah, most people don't use susans in wall cabs.

Round lazy susans waste a huge amount of space. Do you have a choice? Either pie cut or D cut susans make MUCH better use of the space. Personally, as much as I love susans, I am not sure I would install fully round ones. Draw it out on graph paper. You will see what I mean.

Are your cabinets 12 or 15 inches deep? Are they angled or do they run into each other to form an L?

I think I would do without for now and install DIY susans at a later date. Do be sure your shelves are movable!! And order at least one more shelf for each wall cabinet than is standard.

Thanks again. They have already made my wooden Susan's. The cabinet gal will be here tomorrow morning to do a follow up on the details of my cabinets that were installed late last week. I forgot to order an extra shelf for the Susan corner but did order extra shelves for some of the other shelves. You are very knowledgeable and so helpful. Thanks Bellsmom for sharing! I hope others who read this will learn from my mistake before they order cabinets.