[Growler]

Depends on intended usage.

Here's what's in the house right now: one Kindle, one NOOK, and two iPads.

For straight leisure reading, Kindle and NOOK are the way to go - downloads are quick, and they're really just like reading a paper book. Only drawback is, like a paper book, if you don't have light to read by at night, you just can't read 'em well. That said, the digital ink technology is pretty great for preserving battery life. Don't know too much about the apps for either of those two, though.

The iPad is the Swiss Army Knife of e-readers - it has lots of apps, and does a lot of things reasonably well, including ebooks, but it's not a dedicated reader, or a dedicated tablet computer; much like I wouldn't use a Swiss Army Knife to swap an engine out on a car, I wouldn't use and iPad for heavy computer processing.

iPad is backlit, which eats battery a little faster, but allows reading in lower-light than does Kindle or NOOK. iPad is also a heckuva lot more expensive - you could probably get both Kindle and NOOK for the price of an iPad.

If this is your first venture into the ereader/portable arena, I'd say look closely at NOOK and Kindle. Both are good devices, and will serve well.