My wife is not an advanced user of computers by any stretch of the imagination, but I would never buy an iPad for her.
She has a DSLR and 60k photos in iPhoto (~320G). iPads will eventually store this much in 3 years, but you will want it backed up somewhere (and in 3 years the "cloud" still won't be doing this much (personal) data at a reasonable personal cost compared to a physical device). And she will not be tolerant of doing edits or looking at photos on a 10" screen.
Not to mention that once you increase the screen size, portability goes out the window -- you will have a monitor. And guess what? Touch input doesn't really work ergonomically on a 24" monitor.
There are solutions, Airplay will obviously be involved, as will BT input devices. But it's not quite ready for prime-time yet.