The E-grip is fast and fun. X-7 marker is reliable.
Hasnt been released to public. I heard Tippmann had trouble with Egrips at OK Dday.
I went to Special Ops Elite Weekend '07 and on the second day we had the chance to go down a zip line shooting targets with an X-7 with an E-grip and Flatline barrel.
I went down the line and the grip performed like it was supposed to. After a few shots It would kick into either a full auto or burst ramping mode (I don't know because I didn't hold the trigger down more than 3 shots). I love the selector used for choosing the firing mode, you flip a switch from safe to semi to another selection and you press the button you want that selection to be.
I used this at the end of the day so about 45 other guys had used it through the day, and it was still working fine. The X-7 seems to work great, I've been using mine regularly since that weekend and I haven't had a single problem. I have heard other people say they have problems, but I can't speak for them.
When it comes out I recommend that you buy it. It's fun and the X-7 will load up to 20 bps. The E-grip on it will allow you to actually fire that much.