I think so timestamps for only detect form changed records. I use identity columns for keyfields. But don't use identity columns for where clauses. Use your ID for where. Because VFP can't know value of identity columns until requery().
Oh!.. Timestamps was madden me... :(

Read Microsoft's recomendations about timestamp:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_ta-tz_6fn4.asp

http://support.microsoft.com/default.aspx?scid=kb;en-us;138809&Product=fox