I'd say that seems to cover both bases for not needing a VM.
Every language should have something as simple as these. Heck, it should be part of the OS, IMO; why I can't (easily) run two different versions of Firefox with two different profiles at the same time is beyond comprehension.
* Install your different Firefox versions in different locations (so one doesn't overwrite the other)
* Use "firefox -ProfileManager" to create at least one different 'profile', which is Firefox's user data set
* Use "firefox -P <profilename> -no-remote" to launch Firefox. -no-remote allows multiple Firefox instances to run on the same machine. -P profilename is necessary because you need a separate profile for each running instance.
Ooh, I'll have to try that. I've been using different profiles, but didn't know about the last step.
Still; mindboggling. Different version = different binary launched, which accesses a different and non-locked profile. Why the hell does it instead open a new window of the currently-running version?
As a heads-up to anyone considering this: Sync doesn't (currently) like multiple versions. 3.6.10 won't sync now that I've hooked up some 4 betas.
You do need a VM if you use memcached/redis/some other thing and don't want to install it on your machine. Other than that (for 90% of cases), virtualenv has you covered.
A VM is a constant time investment, doing it for every language is linear with the number of languages.
Unless there's some serious increases in clock speeds, I'm not sure doing it for every language is worth it. As it is, VMs are a great, general purpose system that are easy to set up, use, and replicate.
