Some more differences:

---With Webi 6.5, use of multiple data providers are allowed.....but the the only problem is that there is no syncronisation..i.e, Data providers cannot be linked!

---with 6.5, infact from 6.1 onwards, you can directly save a report into .xls, .pdf, .rtf...etc formats.

---there is a lot of improvement in Application Foundation with many new features