Well for my comic art, I use flash mx2004. The reason the lines look like that, is that the brush tool automatically smooths the lines. Flash is great for drawing cartoon or comic art but it's limited because it isn't a bmp-based art program like Photoshop and also has limited brush selections.
For my sketches I've been using a trial of Photoshop and to get smooth lines I just use large sweeping movements that take up most of the pad to minimize jitter. However, because of the tablets small size, even tiny jitters are translated to be rather large. That's one reason some artists prefer larger tablets.
If your interested in cartoon or anime art, I'd definetly suggest trying flash. It's really great for cell shading but eventually your skills will outgrow it. Right now, I'm still doing lines in flash but I'm experimenting coloring the same art in photoshop.
Still, flash is a great place to start because you'll get experience with layers, coloring, ect.
Let me know how it turns out