How do I help the performance for a thousand user inserting/updating the same table?

I have an application that supports thousands of users.  From time-to-time, hundreds, and even more than a thousand, will update or insert into the same table within a couple minutes.

I'm seeing a lot of commit-waits and logwriter waits.  I KNOW the best fix is to not let them do that but the software is not written here.  Is there anything I can do configuration-wise to help?

I've already put the redo logs on the best storage I can get.  Would it help to put the busy tables into their own individual tablespaces away from everything else?  Any other suggestions?