paulcole's comment "Are you really ready to stop doing the things you're hiring this person to do?" is a bit on the nose. Learning to let go and delegate is key.
The biggest value I'd say I get is outsourcing decisions that aren't really important but are likely to cause my to spiral into "analysis paralysis". For example, hiring movers - if I tried to do it myself I'd end up spending hours fussing over reviews.
Another major thing is figuring out things I hate doing (phoning people, filling out expense reports, etc) and let my PA handle them.
It's also nice for me that she's British (I'm an American expat living in the UK) and is fairly experienced as an PA/EA and generally knows lots of things that I don't know I don't know. For example, when my partner and I wanted to have a special celebratory meal, she arranged a completely custom menu with a high-end restaurant, which didn't occur to me as something that I could ask for.