I've no idea of the %, but our dining table and 8 chairs, computer cupboard (which I love!), and 2 kids chairs are from IKEA. Have a few kitchen bits too. Also DS2's wooden highchair, a couple of small chests of drawers and a small bookcase. Oooh, thought of more - 2 of the Billy? bookcases in our room, a bedding chest, a chest of drawers in DH's wardrobe.... think that's it
We've had more at earlier stages in our marriage, but they've died due to 6 moves in 5 years! Love it, and if we lived closer (were 1 mile away at one time!), we'd certainly have more of their stuff. We're currently about 3 hours from the closest store.
Other furniture - some rented from the Navy (we decided that it was better to pay a bit every year and have top quality furniture rather than constantly falling apart stuff), some inherited from parents, some solid stuff from Ebay and a v.expensive set of lounge furniture including sofas from Klaussner (who went bankrupt without filing the paperwork for our guarantee )
It sounds like a lot of IKEA stuff, but it's not the typical bits, and apart from the bookcases, I wouldn't say that any of it was obviously IKEA furniture. Wish we were a shrine to that sort of ordered tidy living though!