I have tried to migrate from a 750 to a 750G. Both are running ros 4.5. I made a backup, then copied the backup to the 750G, then restore.

When I plug it in as a replacement, it doesn't work.

Then when I log in I notice that there are slight differences. Ether1 has a different name than before, etc.

Shouldn't I be able to copy configs between devices?

No. Backups ("/system backup") should only be restored on the exact same system.

http://wiki.mikrotik.com/wiki/Manual:Co ... Management

The restoration procedure assumes the cofiguration is restored on the same router, where the backup file was originally created, so it will create partially broken configuration if the hardware has been changed.

From the same link you can learn how to do a text export instead. That will still need editing before pasting it into the new router, e.g. it hardcodes the MAC addresses.

yes, just like Fewi said, you have to use Export and manually edit it, to keep only the things you really need applied

Normis, did you think about some 'no-defaults' parameter for /export command? so one don't see 'disabled=no', 'max-limit=0/0', etc in config... like you did with comment="", but for the rest values =)

So, is there any recommended way of transferring configuration backups to another (for example spare) router because the original one went up in flames? other than exporting config and fiddling around for half of an eternity to get all the mac-address related stuff and so on out of that file?

with ciscos you can just copy the running-config file of some other router into the startup-config of another without too many headaches (actually, none at all).
every time I try to import an .rsc file I exported from another router it horribly fails because of some stupid crap (like /ipv6 nd - killing the import saying it already has such an interface).

although I did transfer some .backup files within several routers of the same type (eg. RB433UAH to RB433UAH) and that seemed to work fine. Even with slightly different RouterOS versions (4.5 vs 4.9)

Can backup files be used interchangeably between same models ? i.e. 750G -> A differnet 750G ?

i assume so - i could do it within several 433UAH without any special problems (apart from having duplicate mac addresses)

It's not guaranteed. Any time you change hardware (even among the same models) things can go wrong.