Jan Goyvaerts has introduced some key information about Unicode in Delphi 2009.
http://www.micro-isv.asia/2008/08/get-ready-for-delphi-2009-and-unicode/
Marco Cantu has made a performance comparison between AnsiString and UnicodeString.
http://blog.marcocantu.com/blog/tiburon_unicode_video_5.html
Conclusion
According to the information, so much I have collected in the past a few months, I summarized them as the following points:- Simple projects can be upgraded to Delphi 2009 without any modifications. Projects with heavy string operations or file operations could be compiled as well. But they should be tested completely before release.
- UnicodeString is based on the same concept as AnsiString. So it is very fast and efficient, although it is a little bit slower than AnsiString.
- In compare with WideString much less memory will be allocated for UnicodeString. If it is not necessary, you had better switch WideStrings to UnicodeStrings for a performance boost.
UPDATE 1: Here and here are detailed performance tests
