Views 1 views stored in the database may not convert properly to Views 2. In order to aid with the conversion, a tool is available. In the main Views page, choose Tools -> Convert. Any views you choose will attempt to convert.
Note that converted Views may not match perfectly! Adjustments may be necessary to retain the integrity of your previous views.
Views 1 views may also be exported before upgrade, and then imported through the standard Import tab. Those views will attempt to convert during import. Exporting your views before upgrade has the added benefit of ensuring a backup.
There are no known issues converting views from Views 2 to Views 3 at this time.