These records are, unfortunately, behind the NEHGS membership firewall. However, I am a member, and many libraries also subscribe to NEHGS and can access the www.newenglandancestors.org site.
The NEHGS page says:
This compilation of Abstracts of New York Wills, Administrations and Guardianships was created by William Applebie Daniel Eardeley. The original materials are part of the Brooklyn Historical Society's manuscript collection. Eardeley abstracted original estate proceedings in the counties of this state. In addition he indexed on 3 x 5 cards all the names in his abstracts, i.e. those of the decedents, executors, administrators, petitioners, guardians, witnesses, named beneficiaries and minor children. The original abstracts were written in pencil on yellow legal pad paper. Although the original title of the collection refers to the years 1691 to 1860, the bulk of the material concerns the period 1787 to 1835. Also, while the abstracts generally end at 1835, it appears that in a few cases the dates were extended to fill a county's file folder. For estate proceedings of counties formed after 1835, the researcher should look under the names of the parent county.
This database currently contains transcriptions for the following counties: Clinton; Cortland; Delaware; Erie-Niagara; Franklin; Herkimer; Lewis; Livingston; Madison; Monroe; Niagara; Oneida; Onondaga; St. Lawrence; Sullivan; Tompkins; Warren; and Yates. We will add the remaining counties from this collection in future.
I looked for my elusive William Knapp (b. ca 1775 in Dutchess County NY, died 1857 in Sussex County NJ) in this collection, since one of the counties listed was Putnam (which was part of Dutchess before 1810 or so). I didn't find him, but did get a pretty good idea of the scope of these probate abstracts. They would be extremely useful as a finding aid to people searching for probate records of New York ancestors.
The images available are of the handwritten abstracts, not the probate records themselves. They are downloadable. I would be happy to search for one or two items if someone really needs help. Please contact me at rjseaver(at)cox.net.