First off, I think Platypus GravityWorks Filter Systems are the bomb! I give this 2.0L Filter System a 2 star, or "not recommended", rating only because I think the GravityWorks 4.0L Filter System is the best backcountry filtration system out there (see my separate review of that excellent product)!
Reason: For virtually the same weight, cost and space in your pack, you get the flexibility to manage up to 8L (with the 4.0L system) vs. only up to 4L (with the 2.0L system) - again, see my review of the 4.0L system.
It seems as if the usefulness of the 2.0L system is for day hikes (and it's presented that way in at least one Platypus product video). In contrast, the 4.0L system can be used for day hikes AND overnights AND weekend trips AND week-long trips, etc.
Reviewers Note: Upon re-reading backcountry.com's product description above, the 2.0L product would be a good choice for solo backpacking adventures. But, for all the reasons I've outlined above, I still recommend the 4.0L system.