1. I apologize for the empty posting with a similar title.
2. I've long since mastered virtual mode in datagridview for doing lots of
things besides what it was designed for i.e. handling large amounts of data.
I have a couple of very clever data entry systems for engineers that make it
look more like a fancy spreadsheet than anything else.

3. So I finally get around to using it for large amounts of data an I am
appalled, just appalled. Response time for data load was horrible. I squeezed
every bit of slop out of the data input and finally pin pointed the culprit
was setting the rowcount.

Since I was doing what the MSDN article on this situation suggested I was
scrating my head. Here follows for the broader community what I posted on the
bottom of that article.

Implementing Virtual Mode with Just-In-Time Data Loading in the Windows
Forms DataGridView Control  
http://msdn2.microsoft.com/en-us/library/ms171624.as

I was not dealing with a large number of rows - about 1000 - but it was
taking way too long to load the grid. The data read in almost
instantaneously; setting grid.rowcount was killing me. (When I set it
arbitrarily to 10000, setting the rowcount never did complete within the
amount of time I was willing to wait, no less under the 3 second rule.)

The cure was simple and not mentioned above as near as I can tell.  It is
essential that grid.CausesValidation = False
be off at least for the time it takes to set rowcount. Makes all the
difference in the world in response time. (I've seen suggestions in other
articles that the number of rows in the grid be limited to a smaill number
but that leads to very intersting navigation problems.)

I have a completely different app where the datagridview is being used as a
psuedo-spreadsheet rather than as a database viewer. The spreadsheet has the
ability to show / hide inactive rows. Toggling this mode was painfully slow
when shrinking - you could wat the scroll change size. Not enough time for a
coffee break, but certainly enough for a good swig. Turned off validation and
problem stuck around. What's the difference - in both cases the grid is not
bound to anything and virtual mode feeds all the data. However, in the first
(fast) case the grid doesn't explicity store anything whatsoever. In the
second (slow) case I am using the grid.rows to store the "data". In
retrospect that was probably a mistake. Ah well, the joys of consulting.
Fixing the speed was on the todo list for the next release.