I'm currently working at Ta Mère SCRL a small development shop in Belgium.
We mainly do mobile apps (iOS, Android) for clients. We also have a strong interest in Pharo Smalltalk and Rust.
From time to time, someone on the Pharo mailing list asks how to build a desktop application.
A long time ago, Smalltalk was a great way to make desktop apps. drag & drop, rich visual interface, mouse pointer. Yeah, the mouse was quite a big thing.
Things have changed. People expect consistency from the software they use. Not only in the look but also in the feel. They want their applications to be tightly integrated with their operating systems. If you’re considering a niche application where people only care about the functional part of the system, that could work. Otherwise I would not bet a penny on a smalltalk dialect.
Long story short, don’t use Smalltalk if you want to be the next WordPad or iTunes.
I’m not saying that Smalltalk is bad at user interfaces, new UI paradigms are tested with Smalltalk. Croquet and Newspeak, Gaucho are examples of some innovations in user interfaces (one for collaborating in 3D world, the other for IDE and GUI framework).