I also got the $99 deal about a month and a half ago. For the most part I love this coil. I am pretty much new to the hobby myself. I bought the ace 250 in march and it's more than paid for itself already. I had only found one silver merc with the stock 6 x 9 coil. Since I got the 10 x 14 I have found 16 more silvers (5 Mercs, 6 Rosys, 4 washinton Quarters and 1 Standing Liberty Quarter (no date). The increase in silvers is partially because of where I was detecting. They were found all in one park but I dont think I would have found most of them with the stock coil. A couple of the quarters were pretty deep. I'd say about 10 to 12 inches. I have heard people say that cranking the sensitivity does not really affect depth but I have to dissagree. In an open field, not so trashy area, I usually crank the sensitivity up to about 7 or 8. If I get an inconsistent 8 inch + signal I crank it all the way and the signal usually becomes solid (just remember to turn it back down). I have found a few dimes and at least two of those quarters this way. The downfall is I have also came across some deep chunks of junk iron that ring up in the quarter to dollar range. I mostly operate in tot lots with the sensitivity at around 3 or 4 as normal. I usually have pretty good luck pinpointing off the "EQ" logo on the top of the coil. This coil definitely covers a lot more ground in a shorter time.
There are only a couple of things I don't like about the coil. One is that it is a little front heavy. The coil tends to want to tilt forward which causes you to tighten the plastic connector bolt and re-adjust all the time. Mine eventually broke and I had to order another one. A couple of small rubber washers usually helps a little. Another thing is that if you hunt for more than a few hours at a time you will develop a nice cramp in your forearm. You will get used to this eventually if you keep switching arms, which is a pain in the butt. Overall I would definitely recommend getting this coil. I haven't gone back to the stock coil since I got it.
Good luck with your diggins,
Chris