I started with a D80 - I attached the MB-D80 grip.
I went to a D300 and attached the MB-D10 grip.
I bought a D90 as a backup to the D300 and to shoot video. I put the MB-D80 grip on the D90.
At the same time that I bought the D90, I "loaned" my D80 (sans grip and with many, many shutter actuations) to my son-in-law a few years back, and he is still rolling along with it.
I shot the D300 for quite a while, with the D90 as backup
I went to a D7000 and attached the MB-D11 grip. Wow, what a difference between that camera and grip and the D300 and it's grip.
I just went to a D700 and attached the MB-D10 grip from the D300 to the D700. This is a beast of a machine.
I will keep the D300 for backup - I've ordered a Zeikos grip for the D300.
I love the feel of the D700 with the MB-D10 grip. The D7000 - even with the MB-D11 grip - does not feel as comfortable as the big D700 with the grip.
It is a load - and it will give you a workout, but I really like it.
My daughter is now shooting the D90 with the MB-D80 grip. I guess you can say the D90 is now also "loaned" out!
I also really like the fact that I shot the D300 for so long, that now the D700 is already almost second nature - there is no comparison between the D300/D700 camera layout/controls as compared to the D7000 - and for the few pictures I have taken with the D700 - I am as happy as a clam - the pictures are just awesome.