I believe you can only do shared care if you are low risk, and if any complications arise you are referred to an obst for help anyway - exactly what would happen with a midwife.
I did shared care last time wiht my GP, but slightly different circumstances. She used to work in the public birthing system in Geelong, and so knows all about what goes on in it. All the midwives know and lvoe her too. So I got more than what the normal person gets I spose?
This time around I am in the Family Birthing Unit (sort of private midwife care) but I have still seen my GP for a few pregnancy related problems to save a hossy visit. She doesn't bulk bill, but its still worth seeing her. We also seem to be at the drs all the time anyway, so she is always asking how I am. I usually request my test results get sent to her as well to be on the safe side.
Also, it does start a nice bond with the GP as you will see them soooo many times after you have the baby - for everything from needles to a runny nose, so we feel like she really is our family GP - and that she cares.

The biggest drawback to shared care is you dont really get any sense of what the birth is going to be like, as your GP wont be there with you on the big day. I think if its your first time, its really important to spend time with the people that will be with you through the birth so you get to know each other, and you feel that you have a level of trust with them.

So I would agree with your midwife - if you feel rushed by your GP, I wouldn't bother going through them for shared care.