You should be OK for the most part. The usenet tables are all prefixed by 'usenet_' and it's unlikely they will ever conflict with a vB table. There are some added columns to the vB tables but again, it's unlikely they will conflict as they only have relevence to usenet stuff.

Where you may run into problems is the indexes. It should be fine when vB 2.0 is finally released, but with each beta I see a different set of indexes on the tables. One major ommission on beta 3 is the unique index on the 'username' column in the user table. This is required if you are importing users from usenet so my script adds it. If beta 4 fixes this ommission, you will end up with redundant indexes.

I can't forsee any scenario that would lead to posts or users being lost or removed so you're safe there.

Don't worry too much as I have this installed on my boards and it will be in my interest to make sure it all works for each new release