oracle 8i release (8.15),(8.16),(8.1.7)????

Are there any differences in Oracle 8i release (8.1.5)(8.1.6) (8.1.7) or they are patches?
I am currently running 8i release 8.1.5. Are there any benefits for migrating to 8i Release 8.1.6 or 8.1.7? Or the new release are only patches?

If I could benefit from migrating from different releases of the same version, what are some of the benefits.

they just add new features in each release, XML,PL/SQL Gateway etc. If you want to know the detail of the new features try technet.oracle.com

thanks pando