The Guardians of the Galaxy Infinite Comics make for vacuous reading. They're not really stories, merely brief character moments. As such they're not very satisfying... but they are free, so there's that.
Moreover, the GOTG Infinite Comics serve multiple purposes. First as a proof of concept for new means of using the digital comics medium. It's not motion comics, but it presents things in a layered, quasi-animated sense, where a background will remain stagnant but the characters will move, or a body will hold a position but a head will look multiple directions. It's actually an intriguing development, one I hope more comics learn to use (I wonder how dependent it is on Comixology's Guided-View (tm) technology?), as it can have added value to the experience of reading the comic, particularly in expanding the action sequences.
The second purpose these GOTG Infinite Comics serve is as introduction to the main characters of the GOTG books (and forthcoming movie). They're bare bones as far as introductions go, but if you're not familiar with the characters at all you do glean just a little insight into them. Gamora in this issue, for instance, we're told (or reminded) is Thanos' daughter, trained to be one of the most powerful fighters in the galaxy. She's rebelled against her father and fights to free those under his sway. That's about the crux of this book, introduce those few points, show her kicking a lot of ass, loop it into GOTG #1...
... Which is the third purpose the these Infinite Comics' existence... they're free, so they're promotional. They're to get people excited for the comic book. Read this, go buy the comic. I mean, we gave four of these to you, so don't you kind of owe us to at least read the first issue? (I mean, I would, but...$3.99? For Guardians of the Galaxy? That movie ain't made, and it ain't a success yet guys).
Finally, this particular book serves to re-introduce Gamora in a, well, less sexualized, less offensive, less impractical wardrobe. Gone is the Euro-style Vampirella-esque body thong, say hello to mesh and body plates, halfway between Tron and an Star Wars Stormtroopers. It's certainly something one could see Zoe Seldana in whereas the former you primarily would only find on a mannequin in an Adults Only shop.