Just a simple script to back up ESXi configs to a file on a remote Windows Server:

Set ESXiPassword=[put your password here]
perl “C:\Program Files\VMware\VMware VI Remote CLI\bin\vicfg-cfgbackup.pl” –server [hostname of server] –username root –password %ESXiPassword% -s [path to .cfg file for backup]

Yes, it’s simple for a single server, but you can enter all of your servers in one place and backup all of their configs all at once.  Throw it into a batch script and run as a scheduled task.