I currently use Manga Studio 4 Debut (the cheaper version) to do my comic
and I'm pretty satisfied with it. It has a bit of a learning curve and doesn't come with any hardcopy instructions (I believe it only comes pdf file) so I had to go online and watch/read a bunch of tutorials in order to get started. Once I figured it out, though, I found it to be exactly what I was looking for.
Many different tones
Many different and easy to use/manipulate word bubbles
Many different and customizable brushes
Adjustable line corrector (this should help you with the "wobbly line" problem)
Great paneling tools
Various pen types
Easy to use and customize Focus Lines/Speed Lines
Clearly marked and measured bleed and trim areas
No eye dropper tool (in the cheap version)
Can't manipulate the tones
Exporting is sometimes a little wonky (I don't know if it's just on my computer but sometimes when I export the file some areas that have a lot of tone get this weird 'plaid' overlay)
I've personally never used the more expensive version but here's a comparison chart: http://manga.smithmicro.com/debut_vs_ex.html
Overall I'd say I'm happy with the program. It was designed specifically for making comics and it really gets the job done.