Always test your newly generated configuration file with sendmail's (-bt) rule-testing mode. Run a series of predetermined addresses through the /parse command and look for any discrepencies that look odd.
Make sure your DOMAIN file does not define operating system-dependent parameters. It should contain parameter and FEATURE declarations that you want all the machines in your domain to share. For example, if you want to include FEATURE(redirect) or FEATURE(nouucp), declare them in your DOMAIN file for consistency across all hosts in your domain.
A new binary should always be accompanied by a new configuration file. Whenever you build a new version of sendmail, be sure to also create a new configuration file with the m4 technique.