As far as I can remember Rev 1d.4 and 2.B can have problems with timing issues but these are only really supposed to manifest temselves with faster processors (040 or 060) and if you expand you 1200 too much (i.e. graphics card, faster IDE etc).
I think you should be ok with the expansions you are going to be using.
Also some floppy disk drives that came with Escom A1200's (these were mostly revision 2.B motherboards) had something wrong with them (as they were cheap converted PC floppy drives) that caused some older Amiga games to not be recognised by the system and hence unplayable.
