I have used Spectacu.la in the past and it has usually worked without a flaw. I had to change to wp-comment master for a while because I was using a different theme and have noticed a difference between the two. Spectacu.la scrolls the page down when you click the reply button. When you post the comment, it scrolls up to the comment that was just posted. I get the idea, but it involves a lot of moving of the page. It also takes you away from the comment you may be replying to, if you need to refer back to what was written.
WP-comment master seems to clone the comment form, directly under the comment being replied to. Is there a way to enable that feature in Spectacu.la?