A Pure Vector Approach as Solution?
A more Painterly Approach
Do we need infinity zoom? For cases like showing the world reflected in a girl's eye, yes. For such cases, people without infinite zoom could simply make drawings at multiple scales and switch between the drawings (which is what people currently do) so it's not really the end of the world.
In Expresii, we don't claim to do everything. We can't do infinite zoom. Our canvas/paper is finite, which is actually closer to a real-world painting experience - you have a frame to anchor your work. Instead of infinity canvas, Expresii offers extendable paper. Our end result is a rather organic looking painting that we can zoom a lot into. The strokes and flows are extremely natural - unprecedentedly natural.
BTW, we are really glad to see a steady growth of GPU hardware. We used to require an expensive discrete graphics card, but now even an integrated GPU can do the job fast enough. Interesting side note: When Nelson was speaking at the Adobe Headquarters in San Jose back in 2006, Senior Photoshop Scientist Chris Cox was bashing the use of GPU. I think he was like laughing at a person building the Internet at its early stage - hey network is so slow, why bother. Well, if you can see the potential early, you will be heading in the right direction. Now, even Photoshop itself is getting more and more GPU acceleration. What would Chris say now?
Best of both Worlds
In contrast, Expresii really gives you the richness of pixel-based tools. You can still blur a stroke (we don't have a separate blur tool but you can do so by stroking with a clear brush or use our new Pusher brush mode), not to mention our extremely natural ink flows efficiently executed on the GPU all thanks to its pixel-based nature. However, Expresii also has its vector personality - you can zoom in a lot as if there's no pixels. We believe Expresii is a true innovation in the history of digital painting, really 'taking the best of both worlds'. Give it a try today and see for yourself!
 from their paper "Industrial-Strength Painting with a Virtual Bristle Brush", 2010. [cached copy]
^ Update 2016-12: development of Mischef seems to have stopped. Founder and Chief Scientist Sarah Frisken even left the new company founded due to the Foundry acquisition. Head of that company Chris Cheung , who moved from Autodesk's Sketchbook, also left the company. Update 2019-10: madewithmischief.com is finally closing in Dec 2019.