You miss out on a lot of modern advancements. A few things that come to mind from my lovely house:

* Single pane windows that leak heat / cool, also that rattle.

* Lack of insulation.

* Non-grounded wiring / unsafe wiring.

* Plaster instead of drywall, cracks very easily.

* Old heating systems (oil furnace with steam radiators).

* Crooked doorways and doors that don't close quite right.