I don't think it will take the place of Dropbox, which I use (and love) -- your Cloud Drive is accessed via a web page or on your Android device, while Dropbox automatically syncs with a directory/folder on your computer; this makes it much easier to move files to Dropbox and you can access your Dropbox folders from you iPhone/iPad (I use this feature to get EPUB's over to the iPad and open in BlueFire Reader, as well as to copy over PDF's that are easier to read there than the Kindle) and from the Kindle (including wirelessly downloading non-DRM'd mobi books, I've been told; I haven't used this feature myself, yet). If you Calibre folder is small, you can just move it inside the Dropbox folder and it will automatically sync to the web storage and every computer on which you've installed your Dropbox account (no more emailing files to yourself from other places). You can also set up directories inside Dropbox that you only share with certain people (I use this to share documents with someone else, so the copy being edited is quickly updated to all involved).
The Amazon Cloud Drive does none of this, but ... it's Amazon, so they have added one very cool feature -- any music that you upload can be played using the Cloud Player from any PC (via a web page) or your Android device (using the Amazon MP3 App). In addition, any MP3 music you purchase (as of yesterday) now gives you the option to send it to your Cloud Drive, rather than downloading to your computer right away. Make sure you pick this option with the next MP3 purchase (it will then set up a default for you, so you don't have to answer each time, which you can change later, if you want), as the Amazon MP3 purchases don't (repeat, DO NOT) count towards your storage limit. I've spent the morning re-purchasing (more on this later) some MP3's and have over 7GB installed, but not one single byte is counting towards my 5GB limit. Once stored on your Cloud Drive, you can either play the music directly from there (streaming) or download it to your PC or Android device.
There are a few limitations: only files up to 2GB in size can be stored and music files over 100MB won't upload using the upload tool in the Cloud Player. Also, you have to use the web interface to download the files back to your PC, unless you go into your MP3 Settings (on the Cloud Player page) and click to automatically download your MP3 purchases to the computer. You can, in fact, open up that same page on any number of computers (an unlimited number, from what I can tell), log in and have that computer also automatically download any MP3's purchased. Essentially, you now have a method of syncing all the computers you use (desktop, laptop, phone and work, for example) with your new MP3 music, with no additional effort on your part.
So, what about music you already have? Unfortunately, Amazon is not automatically adding your past purchases to your Cloud Drive. So, your existing music, unless repurchased via Amazon, will count towards your 5GB limit. If you purchase at least one non-free album, you'll have 20GB to store it in, but I have well over that just on my laptop (and the 20GB must be renewed each year). Amazon will, however, let you repurchase music, so I would suggest that you look thru the current Free MP3 Albums and Free MP3 Songs (I've sorted these by album and you can use the genre tags on the side to narrow down the choices) and repurchase those that you already own. You'll be prompted during checkout that you already own them (for those you do), but since they are free, the only thing this costs is your time. With the first one you purchase, make sure you tell it to send it to your Cloud Drive. Then, when you click on Upload to Your Cloud Drive from the Cloud Player, the music you have already installed will be removed from the total, letting you see if your music collection will fit in the default space provided.
If you need more space, consider picking up one of the 100/$5: 100 Albums for $5 Each or Seed Your Cloud Albums as $5 or less for an album you keep is a lot better than paying for the additional storage in the first year. There are quite a few interesting ones that still have a couple of days left on this month's sale (and there will be new ones this Friday). I've included a few albums below that I discovered while exploring today - two at $5 and three free albums that I had not seen previously (and which are now snugly tucked into my Cloud Drive.
- ...Featuring, by Norah Jones $2.99 (I paid $5 for this one!)
- What's Going On, by Marvin Gaye $5
- Greatest Hits - We Will Rock You Edition, by Queen $5
- Allegro 2011 Winter Sampler free
- Music for Massage, Meditation & Yoga free
- Celtic to Classic - Relaxing Guitars free
Update: It turns out that anything listed as an "album" counts, not just those with multiple songs. So, this album (currently the top selling album at Amazon) will upgrade you to 20GB of storage for only 69 cents:
If you don't like that one, I found this one at the same price:
I didn't cheap out, though, and found an album that I really like (bought and my space is now upgraded!):
