eBooks on iPad

My apologies in advance if this topic has already been covered. My prime motivation to buy the 3G/32 or 64BG iPad is to satisy my insatiable desire to read books. I go through 2 to 3 a week and need to hear how current users of this application feel about the quality and quantity of offerings. Additionally, how does Apple's bookstore measure up in terms of pricing and availability of best selling authors?

iBooks while not anywhere near as extensive as Amazon (yet) is price competitive.
Amazon already has their Kindle reader for iPad, so all of your existing Amazon books can be used... purchased and downloaded on the iPad.

I believe ereader.com, B&N and Stanza are all working on an iPad specific app and shouldn't be long.