Yes, it saves the image to the card.
No, it's not gimmicky.
No, it's not meant primarily for consumer use.
I write raw's to my CF card and small jpg's to the Eye-Fi. The Eye-Fi sends them to the Photosmith app on my iPad. I do all of my culling on Photosmith right there in the field (flagging, color labels, star ratings, etc. Whatever you normally do in your culling workflow).
Then when I get back to my computer I import the raw's into Lightroom using my import presets, then do a WiFi metadata-only sync between Photosmith on the iPad and LR. This matches up the flagging, star ratings, etc. with the master raw's that are now in LR.
Eye-Fi (and Photosmith) are extremely valuable tools that have had a significant positive impact on my workflow.