NickiW - would definitely recommend the sevenaway, it's well worth it. It was originally started for Post Office workers, which in those days included Telecom, and as EDS has the Telecom contract and took on a lot of Telecom staff, EDS staff are also eligible. It is a good back up to other insurance, but worth getting even if you don't get other health insurance, as there are some handy medical benefits on there (I got a cheaper Southern Cross policy, then used sevenaway to prop it up - it has optometry benefits, physio, podiatry, osteo from memory, and an obstettic benefit from memory if you're thinking about going down that path ). Better still though, they have a large number of holiday cottages around the country (often in popular beach areas), like fully furnished self catering units, that sevenaway members can rent for $99/week. You have to go in a ballot for school holiday periods, but families have preference at these times. They're well worth it.
RE Southern Cross, I would take a look at the policies on offer in conjunction with the sevenaway, and decide what will give you the best value for money. Policies with GP cover are more expensive, but worth it if you go to the GP a lot (think there is some GP cover on sevenaway too, but not sure. Also think there's prescription cover to a certain level as well) - I don't, so didn't bother with that level. Hospital only cover means that you won't have to go on the public waiting list for non urgent surgery, which is a good thing! Also, I think the insurance with Southern X from EDS includes pre-existing conditions, which means you can claim for treatment for these on the insurance (usually very hard to get and very expensive if you organise your own medical insurance). Think you have 3 months after you join EDS to join up with Southern Cross (but check that) and get the pre-existing conditions cover, so I would take a look at the policies on offer before deciding.
HTH!