Weren't these all shown to be fakes? http://cgi.ebay.com/1900-O-Morgan-Dollar-VF-Micro-O-Rare-Vam_W0QQitemZ280253400181QQcmdZViewItem ugh
If I remember correctly the Micro O was found to be legitimate for one or two years and fake for all other years. I can't remember which year(s) was legitimate.
I remember reading this a couple years ago. http://www.coinresource.com/news/news2005/pcgs_declares_counterfeits.htm
Yes, the micro O counterfeits are still worth a significant premium, especially if they are in PCGS or ANACS slabs, even more so if they are identified as Micro O on the label. I would think the ultimate would be a NGC slab with the Micro O fake in it. NGC only slabbed 8 of them before they decided they were fake. I don't know how many of them still exist though. They may have been cracked or crossed between 1998 and when PCGS finally decided they were fake in 2005 or returned to NGC under their guarantee after they became accepted as fakes. If I remember correctly the genuine micro O is an 1898-O.