I agree and disagree with Andrew. I work for Telstra and have worked for Optus and IBM. It really depends which part of the organisation that you work. IBM is a big company - this means red tape. Telstra has this and so does Optus - All big companies do. If you want to work on Big Networks, these are the sorts of companies you want to target - Forget working for Cisco or Nortel - these guys just want to just flog products.
You also have to consider the area within IT that you want to work or aspire to work. Operations (good grounding but you wouldn't want to work there for ever) Architecture, Design, Product Development, Systems, Testing ? There are heaps of areas.
In terms of IT Operations, Telstra , Optus, IBM - they are all the same - Obstinate roadblocks