Sorry about that, peter_watt, I guess I was so caught up in the success of regaining the use of my mail exchange account I didn't realize the massive number of interval posts. I did go back and review, and in case this helps someone, here is my experience.
My issue was initially with NO inbox deliveries, and the above solution (deleting exchange account, rebooting, reinstalling, rebuilding) worked. (Thanks to Karim2u and JLinden7 from way back on page 8). Rebuilding did take quite a while, however.
I had previously experienced slow delivery with exchange in Mountain Lion, and had already followed the suggestion from dianeof oregon and others to not have inbox subfolders, and limit the size of inbox itself by moving older mail to subfolders. This issue continues to be present, as my iOS devices receive mail well before Mail does, and I suppose I have gotten used to the delay. BTW, I recall that I had to rebuild my exchange account after upgrading to Mountain Lion as well, so I really should not have been surprised. Fool me once, fool me again I suppose...
RandyKates seems to have had the inside track in getting a real fix to this issue, and I will be curious to see the outcome. Keep posting, Randy!
Thanks to all and I hope there are indeed better times ahead.