We've noticed that a webgrid with around 1000+ items really starts to slow down with IE 8 but hasn't really been affected on IE 7. This seems to be a problem both on load and on mouse over. Can you confirm that if we upgrade to a later version that you've addressed this issue?
and if so is the upgrade path to 2009 going to be a problem. Or can we just upgrade to the latestest 2008 patches?
This sounds like a scenario that was fixed in a service release for NetAdvantage for .NET 2009 Volume 1. This is the earliest version for which we're targeting support for Internet Explorer 8. The maintenance period of NetAdvantage for .NET 2008 Volume 1 expired prior to the release of IE 8, so upgrading to 2009 Volume 1 or later is likely your best option.
i've tested the new webgrid 9.1.20091.1015 and tested it on IE8 and it actually loads slower then our current build with 2008 controls.
When is your next patch release? Hopefully you'll have some fixes in there.