Much of what I do in Python is text processing.  My largest Python project to date was an IDL which spewed out loads of text; I've also written an HTML formatter or two.  I seem to do an awful lot of string concatenation in Python, and I'd like it to be fast.  I'm not alone in this, as there have been several patches to Python in recent years to speed up string concatenation.

Perhaps you aren't familiar with my original justification for the patch.  I've always hated the "".join() idiom for string concatenation, as it violates the "There should be one--and preferably only one--obvious way to do it" principle (and arguably others).  With lazy concatenation, the obvious way (using +) becomes competitive with "".join(), thus dispensing with the need for this inobvious and distracting idiom.

For a more thorough dissection of the (original) patch, including its implementation and lots of discussion from other people, please see the original thread on c.l.p:
http://groups.google.com/group/comp.lang.python/browse_frm/thread/b8a8f20bc3c81bcf
Please ignore the benchmarks there, as they were quite flawed.

And, no, I haven't seen a lot of code manipulating Unicode strings yet, but then I'm not a Python shaker-and-mover.  Obviously I expect to see a whole lot more when Py3k is adopted.