However, there is something about indexes - if I recall correctly, if you restore a v7 backup to v8 and wish to benefit from the v8 type 2 indexes then you will have to drop and recreate all indexes.
Another thing that comes to mind is that if you have data fragmentation, you can take this opportunity to remove it by export-load though ofcourse, it will be a slower process. There are other challenges to using this method if the system is MPP.