Damn, I figured they'd add book rentals to Prime, didn't think it'd be this soon though.
The one per month limit is pretty lame, especially when video streaming is unlimited. Hopefully that gets bumped up soon. Two would be nice, three would be awesome, four is probably as many as I'd ever use.
This pretty much cinches me getting a Fire. I was already pretty much on board, my free student Prime is about to expire and I was planning on getting it anyway, so I'd already have a subscription to get the video streaming and cloud service and whatnot. Now that I also get book rentals for my Kindle it's pretty much a no-brainer for me.
Prime is a pretty damn good deal now too, 12 books a year is like ~$90, and then the video streaming.
I expect we will see the per month rental limit go up really soon. As long as they only let you have one at a time I really don't think very many people are going to blow through more than a book or two a month anyway. Some people will, but then some people will sign up and check out three books the entire year. I expect it'd be a lot like a gym membership, sign up for Prime book lending to get you reading as your New Years resolution and then forget all about it three weeks later.