I must admit that I've gotten laxer using the inversion table - maybe a few times a week on average. Even though it does feel very good and clearly helps for the recent disc problem I've developed, primarily I'd say I do it for emotional/mental benefits.
It helps with mental clarity, circulation and definitely helps relieve stress. As I say, I've been doing either yoga headstands or table inversions for the last 30 years and crave it if I do without for too long. If you're looking for earth shattering testamonials, I'm not sure you'll find them with inversion tables. The benefit is more long term and systemic to do with increased bloodflow, oxygen and circulation. It's a wellness/prevention benefit moreso than a front line cure for some disease or other - at least as far as I'm aware of.
EDIT: One of the reasons I use it less might be that it's less comfortable with the high blood pressure I've developed recently. Though if you're careful to ease back when you feel too much pressure, it's quite manageable even with HBP.