I've seen at least one script from you and the finished product (and vice versa

) but haven't noticed any issues.
A couple of thoughts:
- As has been said, it is always handy to give a script a final polish once the art is in although that might not always be possible. However, if there is plenty of lead time you can always ask, if deadlines are looming...
- You might just be too close to the process to be truly objective
I think a more worrying reaction to seeing your work in print would be thinking that you can't get any better (whether that is from raging optimism or pessimism).
However, unless you are the top of the comic writing game*, there is always room for improvement - the annoying thing is that early on we all come on in leaps and bounds as we learn from our silly mistakes and school boy errors, unfortunately it is the later fine-tuning that is both the most important part and often the trickiest. You'll know there are areas you want to improve on but pinning down what they are and how to go about the polishing just gets harder.
You've got my email address, if you want let me know if there is anything you specifically want feedback on comparing the script to the finished page and I'll sharpen up a scalpel.
* And even that is subjective, Alan Moore has his detractors...