I used a Eye-Fi Pro X2 for some days and this are the things i remember
Pro:
-Easy Hot-Spot-Setup (b/g)
-Fast Jpeg transfer ( around 5sec)
-Good RAW transfer (around 14-17sec)
-Good "overall" performance
-geotag works quite well und fast
-very much/fast Firmware updates/improvements
Contra:
- i was unable to set up an AD-HOC n-draft transfer
-i was unable to set up any AD-HOC transfer (tried with 2 Laptops)
-stops transfer when new photo is send to the card by the camera
-support-forum is near "non-existent" a request has not even answered in more then 2 Weeks
-becomes very warm over time when "bursting" raw photos to the laptop
Additional:
A 1min K5 Video(around 500mb) took a bit more than 6min to be transfered to the laptop.(That why i would like to have n-draft)
You can insert different photo-stocks like flicker or so to upload the photos directly to your account to keep people up to date about your work.
I used it together with FTP-Software and a Server to send the pictures as fast as possible to my girlfriend, to judge me and my macro shoots properly
When you are in a bigger city with a larger amount of public access-points or several access-points of a certain carrier you can configure the card to use these access-points to send the pictures to a Eye-Fi online-storage or photo-stock site(like flicker).
You can even use you Login-Username/Passwort for non-public Access points which are provided by some carriers (eg. Telekom in Germany)
Conclusion:
For me, in my home-studio it is very good and usable, but, i am a bit disappointed that i doesn't worked out with the ad-hoc n-draft transfer, but i think it will be "fixed" later by firmware or you need some special/distinct setup to make it work.
I would buy one in a blink of an eye, but for me as a student it is too expensive.
The overall usability is very good and reliable but you have to take in consideration that when you are shooting a lot and don't have much breaks the transfer will be delayed!
I testet the range of the x2 and together with a LinkSys WRTG 45GL I managed to get 20-30m, a stronger Accesspoint or a better antenna would extend the range very much(for the guys 30m aren't enough)