As the iPads been on the market nearly a year, It's actually surprised me that it's taking so long for even one iPad competitor to even come out the gate yet.

This has given iPad a significantly huge devoted user base + software app advantage. Any competitor will have to play catch up quick.

Of the competitors, I find the Galaxy Tab the most formidable challenger, but I personally prefer not to be tied to a phone contract with a larger tablet like device.
I prefer reserving a much smaller easily pocketable smartphone for that. I find the iPad size idea for books, mags, pdf manuals, lyrics and lead sheets, email, skype voice, and internet media consumption, including coveniently reading and posting here on sz from just about anywhere I am during the day.