Because the form is connected to products sold via JigoShop plugin, I had to leave the JigoShop plugin enabled.
Out of curiosity, I grepped the JigoShop code for 'wp_mail_from_name'....and there it was a call to add_filter('wp_mail_from_name'.....) without a corresponding call to remove_filter().
Once I removed the call to add_filter() from the JigoShop code, the "From" field is populating correctly. The add_filter() call in JigoShop is redundant anyway, because every invocation of wp_mail() from JigoShop sets the "headers" field anyway.
Thanks for your help. Contact Form 7 is a great plugin, good work.
Phew...that was my first foray into Wordpress code. Thank you for the guidance!