As I spent a little more time thinking about writing a program for solving Sudoku puzzles, I realised that I was giving Smalltalk the go-by for a pretty flimsy reason: my lack of familiarity with two-dimensional arrays. Then it struck me: use an array of arrays (duh). Once this hurdle was out of the way, the rest was pretty straightforward (except for the GUI; I am not very comfortable dealing with value/domain models yet, so this is yet to be tackled).
I am glad that I went ahead with Smalltalk because I am pretty sure the same effort in Java would have taken me much longer. The ease and benefit of incremental coding and testing (the Workspace really comes in handy for this) was really striking.