I shoot with D300 (not the D300s) for a while, I don't own it. Now I have 7D. Beside all ergo, menu, button layout .... things that N and C users swear by each brand, there are 2 things in D300 worth mentioned, I think the same applied for D300s:
1) D300 definitely sealed better, especially battery door, CF door, connection cover. After seeing the D300 implementation, I highly doubt 7D is sealed camera.
2) D300 has spot meter link to AF points, 7D still don't have this.
7D has much better implement on live view, not sure if D300s make any improvement in this aspect.
I like D300 AF point coverage better, almost entire viewfiner cover, very nice.
I also like how D300 grip is attached to the body. 7D with grip is definitely NOT a sealed body anymore.
Other things are pretty equal between the two. Honestly, if I were to start all over today, I will probably pick D300s over 7D, not because of D300s is better than 7D, it is more like Nikon's concept and upgrade path seems to better for me. I like D700 feature set much more than 5Dii.