to me, it's the features and the build that makes d300s a semi-pro. while d7000 is more of a serious enthusiast camera.
there r certain features that d7000 lacks, such as the menu banks, the 2 terminals at the front (flash sync + 10 pin remote terminal), and also the build of the d300s is better than d7000 (full magnesium alloy body vs partial magnesium alloy body). the ergonomics on d300s is better than the d7000 with more shortcut buttons. the AF performance on the d300s is also faster than the d7000, with more points as well. lastly, it also has higher fps (7 without grip, 8 with grip) for fast action shooting. the buffer on the d300s is also larger, allows u to take more burst shots at its effective fps range. lastly, d300s also supports CF card, which has higher write speeds compared to SD cards. how fast the images can be written over to the card is crucial to burst shooting, so tat the buffer will not be filled so easily.
although d7000 is not rated as a semi-pro camera, it does not mean tat professional photographers will not use it for their work. as long it can produce results, i suppose tat's all it matters.
no doubt tat d7000 has higher MP, better performance at higher iso and better video. the specs r tempting indeed, but i believe how comfortable u r with the camera and whether it can satisfy ur shooting needs r more important
