Virtual machines have been a huge win, and still are.
Spending 2-5 days setting up a development environment, then archiving a copy of the whole VM made some of the crappier setups usable. Back before rented software (including the OS) that meant one person could grind through the whole OS/tools/IDE/libraries stack and get something we could all use. I've broken software protection to make this work, because it's just such a huge productivity win.
Being able to have a whole test matrix worth of systems virtualised also helps. One place we interacted with MS-Office, so the matrix was Win95/98/Me/XP/2000 (etc), then three versions of Office {cries}. It would have been just unreasonable as a small company for us to have and maintain 2-3 copies of that matrix as physical machines.
I remember when I switched to Linux around 2004. Compared to Windows XP, setting up anything became minutes instead of days. Because everything was just so much simpler to automatr and so much faster in general.
Freezing and archiving the VMs used to build a particular release is also a pretty nice trick.
It comes in very handy for those rare times when a major customer that (for some reason) insists on sticking with an ancient, obsolete version of your software desperately needs a critical fix.
> Freezing and archiving the VMs used to build a particular release is also a pretty nice trick.
An essential trick if you have long-lasting products. I've been able to (and asked to!) make fixes in ~2015 to code that was written in Turbo Pascal 6. With firmware for embedded devices it's more necessary and often also harder, because often the hardware to flash the firmware doesn't work with new computers. Or you end up with a chain of USB-Serial adapter to serial-to-weird adapter to "programmer board" to actual device... but I knew that when I carefully packed everything into an antistatic bag 10 years ago :)
Spending 2-5 days setting up a development environment, then archiving a copy of the whole VM made some of the crappier setups usable. Back before rented software (including the OS) that meant one person could grind through the whole OS/tools/IDE/libraries stack and get something we could all use. I've broken software protection to make this work, because it's just such a huge productivity win.
Being able to have a whole test matrix worth of systems virtualised also helps. One place we interacted with MS-Office, so the matrix was Win95/98/Me/XP/2000 (etc), then three versions of Office {cries}. It would have been just unreasonable as a small company for us to have and maintain 2-3 copies of that matrix as physical machines.