(I've often said around here that things would've worked out better if there wasn't such a barrier between stuff happening in Smalltalk and outside in the OS -- community wise. But if you're willing to play just in the Smalltalk sandbox, it's a pretty awesome experience.)

I've only used Smalltalk/V during university, back in 1995, if memory serves me right.

I've seen integration problems migrating code between implementations, lack of proper support for source control specially in distributed teams, lack of integration with the operating system for desktop applications.

I know that many of these problems have been solved in newer implementations, but maybe now it is too late.