Don't feel bad about becoming better and wanting to update pages..
I think Tapastic is a great way to test the waters with your comic and become a better artist.
I started Mighty Glad back in February and have learned a lot of what is and isn't working both visually and in the writing, and what I need to work on as an artist.
This site is an amazing tool, keep growing and update your art as much as you feel, just don't obsess or over think it too much though, know when to call it good and keep moving forward.
ding