I think I have officially heard it all...
I vote tacky on the envelope addressing issue. I went out and bought you (generic "you" of course) a gift and came to your little shindig and you can't even address an envelope? Ya know what, ladies have been having babies for years and have been able to find the time to address thank-yous, consider it part of the rites of passage of motherhood.
I recently attended a baby shower for a woman who wasn't physically at the shower because she lives out of state and didn't get a thank-you.
Call me a thank-you piggy, but that is tacky.