How do I get VMware Workstation 10 to switch rapidly between machines?"

With 24GB of RAM I'd not expect it to be an issue, but if you have enough VM's open that they all can't be assigned their full complement of memory, then you'll encounter a paging delay when switching between machines.

But as long as that's not the case, Workstation should switch in less than a second -- at least it does for me.    I've got VM's for just about every version of Widows -- MSDOS, Win3.1, WFW3.11, Win95, Win98, Win98SE, WinME, Win NT, Win 2000, Win XP Home, Win XP Pro, Win XP x64, Win Vista (every version and in  both x32 and x64), Win 7 (every version and in both x32 and x64), Server 2003, Server 2008, etc.    As long as the total assigned memory of the currently open machines doesn't exceed my actual RAM, I can switch between them in well under a second (not in "the blink of an eye" ... but certainly fast enough to not be frustrating).

How many VM's do you keep open simultaneously ??

Generally I have 2 - 4 VMs open.  I am quite conscious of the memory issue and open Task Manager on the host if it goes any higher to make sure I'm not exceeding VMware's recommended 19.4 GB aggregate.

My suspicion is that Workstation 10 is not playing nice with my video card.  Part of the rationale here is another issue I found, that is that I can no long use Aero with Vista after upgrading to Workstation 10.  I never cared much for Aero in the first place, but found that my Vista machine ran slightly *faster* under Workstation 7 with it turned on.  My theory then and now was that Aero somehow made it play better with the video card.  If I now posit that the video card has been taken out of the loop altogether, then both the Aero change and the VM switching time increase are explained.

If I am right, then the question is what to do about it?  According to VMware documentation (http://www.vmware.com/pdf/desktop/ws10-getting-started.pdf), the graphics card should be "ATI Radeon HD 2600 or later".  It would appear at first glance that mine should qualify.  What then is the problem?

I'm afraid I can't comment on the video issue ... although your thoughts do make some sense.  The only way I know to confirm them is to try a different video card.   I'm  a bit surprised that it would make a difference, however -- that's a very nice card !!

I am loathe to try another video card because (A) I don't have time, (B) I can't afford it, having lost my job since this "supercomputer" was built, and most of all (C) I am deathly afraid of deactivating my operating systems.  Deactivation of the current version in each case I could handle, but if that goes down so do all the snapshots.  I'd rather live with the latency, at least for now.

Your comment that "...  I can no long use Aero with Vista after upgrading to Workstation 10. " definitely makes me suspect that the issues are related.    Have you confirmed that you're using the latest drivers for your video card?

By the way, changing video cards will NOT trigger a re-activation requirement for your OS (or any of your virtualized OS's).    The VMs won't even "see" a different card -- they'll be using the virtualized VMware video card.

But I suspect you don't actually need a different card ... just a different driver for your current one.

I found what seems to be the most recent driver install, "13-12_win7_win8_64_dd_ccc_whql.exe".  I now have a ton more options in my Catalyst Control Center, including "Multi Desktop", but the VM switching behavior hasn't changed :(

Is Aero working okay with the new driver?

I actually hadn't thought to check, but alas there is no change in the Vista behavior either.  Attached is a screen shot of a small form such as I would see when Aero is on.  That green halo surrounds every window.  You can say that there are adjustments within Vista that will fix this, and you might be right, but nothing was adjusted from the hour before to the hour after Workstation 10 was installed, and that's when this started.
Aero-halo.png

It'd be interesting to know what a different video card would do ... but I know you don't want to swap it out and can certainly understand that (costs both time and $$).

Another thing you could try -- but it may or may not help -- is a few different versions of the video drivers.    Sometimes older drivers actually work better ... the drivers are unified for several cards, and your specific card may not need some of the newer features.

In the comment I accepted as "the solution", I said that I would give garycase 250 points "if nothing better came along".  Due to a miscommunication with the Admin, I wound up having a 500 point question, and so could not accept garycase's solution outright.  That is for the best anyway since future readers of this question would not see in his remark any actual solution, but merely a question.  I think in the end the solution went the opposite way garycase expected it to:  Improved performance by turning OFF 3D acceleration.  garycase was ready to continue the work, delving into older drivers and whatnot, but right now I need to get back to serving my clients and accept this good-enough-for-now solution that does not pose undue risk to my capital (my computer installation).

I'm giving this "solution" a "A" grade just in case any of that grade would wash over to garycase, who has been absolutely wonderful.  If I were grading myself, it would be a "B" at most.