I just purchased a 3G I-Phone 2/8/09 and bought the trails app a few days later.
I have a Garmin GPS V that I use on my ATV Rides and am happy to say that I have both units working with the every trails web-site and they all work as they are supposed to.
I can send tracks that I have recorded on the garmin to the web-site and tracks that I have recorded on the I-Phone and uploaded to every trails back to the GPS V as a new track.
The pictures that I take during a recording with trails are being saved in the I-Phone Camera Roll and can be loaded to your computer with the USB connection, they can then be uploaded to the trip on Every Trail.
My hat is off to this system as it will give ATV Riders a good way to share their trips with each other.
I have 2 trips saved to the Web-Site now as a test one by my I-Phone and the other by myGPS-V.
You are welcome to look if you like.
http://www.everytrail.com/my_trips.php