Virtualization

It is because drivers need to run in the kernel memory space and as far as I know none of the application virtualization solutions will support any sort of kernel virtualization.

I would say they are bad candidates but some may work, I can only speak for Altiris's Software Virtualization Solution (SVS).
Some may work (most of them not) depending on if they are loaded after the filter driver and any dependend system/boot drivers would also have to load after the filter driver. The virtual application must also be set to autostart. USB device drivers are bad candidates as they seems to load before the filter driver. We have had many discussion regarding virtualizing drivers at the Altiris forum.
Virtualize some printer drivers have been done with success but there also seems to be some problems with PostScript printer drivers.

So in general I would not focus on virtualizing applications including any sort of drivers, they are real time killers.

With SoftGrid I would recommend using something such as DPInst.exe from DIFx to attempt the driver install and remove the driver from the sequence. The problem with device drivers is even though there are tools to simplify the process DIFx still isn't a silver bullet depending on the driver you have to integrate. I would agree with AngelD that they can be real time killers so you should be going into this sort of packaging if there is a significant cost benefit to do so.

I think a mix of using a virtual application with real installed drivers should provide a workable solution. In this way the virtual application will use the drivers outside of the layer (SVS) or SystemGuard (SoftGrid), don't you think Kevin?

I know it does work with SoftGrid with most of that experience being copy protection such as Sentinel drivers. I would assume it would work with other virtualization products as well because I haven't heard of an application virtualization product that doesn't let you talk to device drivers. As a best practice I would go out of my way to remove the device driver files and registry out of the virtual application to ensure that the application can see the data of the properly installed driver just to be safe.

Kevin - Have you tried this DIFx method with Adobe Acrobat 8? Just curious...

I can't remember the specific version because I think it might have been 7 but I was able to get the distiller driver to install with DPInst.exe from the DIFx toolkit.

I think Kevin was referring to install the driver outside of softgrid such as SMS as he stated at http://itninja.com/question/how-do-you-roll-out-new-machines?4288&mpage=2

I'm more interested in using DIFx (or that type of tool to push drivers that SoftGrid doesn't handle) in conjunction with a sequenced SoftGrid package. I reading about the tool now & have asked others in the SoftGrid community for feedback. If this tool allows for on demand use through scripts & integrates with SoftGrid - I'm excited.

Well, the DPinst.exe tool and/or DIFxApp merge module is used to install drivers to the driver store so it is ready to be installed when a user plug-in the hardware. So you could say it has on-demand similarity.