How common are Intel igb NIC drivers/cards, compared to Intel e1000, etc.?

According to this link: http://www.intel.com/support/network/adapter/pro100/sb/CS-032498.htm

These are server based nic's. Having said that, some desktop systems use the the igb driver as well. The 82576 is hardly aimed at desktop use. It's stated to be for dual port NICs and virtualization. What NIC model/chipset do you have?

Edit: You've stated you have the 82576.

The Intel 82576 Gigabit Ethernet Controller provides high- performance dual-port gigabit connectivity in a multi-core platform as well as in a virtualized platform. In a multi-core platform it supports different technologies including Intel® QuickData Technology, MSI-X, Low Latency Interrupts and others, that help accelerate the data across the platform thereby improving application response times. In a virtualized environment it supports Intel® Virtualization Technology1 for Connectivity that helps improve the I/O performance by reducing the I/O overhead on a virtualized platform.

I'd expect better. I think the problem is likely the igb driver. Especially if you don't see issues with these cards/nic chipsets under windows.

I suspect he reason the driver is so terribly old is that it's tied to an the kernel version that ESXi is based on. It would be a similar story to XenServer. Even the latest version of XenServer is using a 2.6 series and a distro based on Centos 5.6. It's horrendously old but well tested. There's a good bet this is the reason.

XenServer provide a DDK to allow you to insert other kernel drivers. Do VMWare provide the same sort of facility?

Perhaps the update provided by VMWare may not be available in the normal update channel because it's not been thoroughly tested? After all, what they are providing is a backport of the driver to the specific kernel they are running with ESXi.

Reading through some of the release notes of the igb driver and there were numberous bug fixes. Some of them affecting performance. Some fixing broken features. Some enabling features that are turned off by default.

By the way, in answering "How common are intel igb NIC vs e1000 etc? Very common. I've even seen them on some reasonable desktop motherboards.