I don't regret upgrading for even one second. I had an S6, and pre-ordered the Note 7. After the recall, I was forced into downgrading, so I got the closest thing (spec-wise), an S7 Edge. When the Note 8 was announced, I preordered (unlocked), and was fairly happy with it. The only reason I say "fairly" is because it didn't really "stand out" above the S8, other than the S-Pen. However, with the Note 9, there are several ways it's better than the S9.
Not only does it have the S-Pen, but the new S-Pen is a considerable improvement over all previous S-Pens. Then there's the increase in storage option...a whopping 512GB. Of course, with that storage increase also comes a RAM increase (8GB vs 6GB). While the camera specs aren't much different, in regards to holding the phone, the side-by-side layout is superior to the over-under layout of the S9. While some are (poorly) attempting to claim that the Note 9 is a relatively minor "upgrade" from the Note 8 and/or S9-series, when one takes a serious look at everything, only then do you truly street setting the actually improvements. It might not be a "revolutionary" upgrade, it IS enough of an "evolutionary" upgrade tho make the switch VERY-WELL worth it.