These migration and compression tests were done a while ago, before 10g R2, when we started to think about moving very large historic databases to Linux and to use compression to save storage.
Since then I have seen several very big databases holding historic data being migrated to Linux using Oracle compression, the benefit in terms of storage is huge with ranges of compression between 85 to 90 %, depending on the amount of repetitive data found inside the Oracle blocks. There is also a performance benefit for data queries as less blocks are needed to retrieve more data.
The companies where this project was later implemented saved a lot of money also by moving from expensive machines to much cheaper Linux boxes.
If you are interested on migration to Linux and historical data compression, this document provides details on both: 10g Migration to Linux and Compression Tests