Played a bit with BeamApp today.
I heard about it on a recent episode of Brett Terpstra's Systematic podcast, and downloaded upon his urging that it was good and that it probably wasn't going to be free for very long. As of this writing, both clients are still free.
Ended up using it not more than 20 minutes after install to beam over text of a photo caption I wrote in an app but for boring reasons needed to use via the Squarespace site on my MacBook Air instead.
For fun, I then tested beaming directions from Google Maps in Google Chrome on OS X to my iPhone. It opened immediately in the native Maps app with both destinations intact. Firing over the play position from a Music app track on iOS to iTunes on OS X worked as well.
For me, the main appeal though is the text beaming. Previously, I would add exchange bits of text via a "scratchpad" text file synced through Dropbox. Going from iOS to OS X with a custom Drafts action is quick enough, but the reverse was rather tedious. BeamApp is faster in either case. As a bonus, I don't have truly temporary things stacking up somewhere that needs periodic maintenance. One less "inbox" to check, in the GTD sense.
For many people, I imagine this could replace a pattern of emailing bits of text to yourself to move it between devices.