When the Xbox 360 S was announced, Gamestop setup a trade in offer that was originally supposed to be good until the 18th of July.  Gamestop has taken down the offer.  Checking their website confirms that it has been removed.
 
For those who were hoping to trade up their existing 360 for the new 360 S may be severely disappointed.  Although, I'm sure some store somewhere may not have been notified of this change so if you have any luck doing the 360 trade in deal, post up what store is still upholding the deal in case any GB users live near that location. 
 
*EDIT*
 Found the Google cached page that shows the offer was good until July 18th.  This page was cached on  Jun 27, 2010.  LINK
 
*EDIT 2*
@JJWeatherman: Found an article about the ad confirming the deal's removal. 

@sixghost: Gives a quick summary of why the deal was removed:

" No, the problem was that the deal was requiring you apply the credit you got from the trade-ins toward a 360 slim, but they are so backordered on the slims that people wouldn't be able to get their Slims for 2-3 months.  "

Interesting. I bet they would still give anyone the deal if you were to pester them enough. That's kinda shady business if they were to post a specific stop time for a deal and then not follow through with it.

Found an article pretty much confirming it. I guess it's because they are too backed up on preorders and so since you aren't able to preorder or strait out buy a new Xbox 360 S, the offer is no longer valid. So basically Gamestop is getting off on a technicality here. Crappy.

" @JJWeatherman: I agree.  If they were committed to making a deal till the 18th they should have stuck to it.  My guess is that the demand for the 360 Slim is a lot more than anticipated and they're realizing they may not be able to get rid of all the older 360's being traded in. "

Crap sake..i didn't even know it officially started...i just heard about it when it was a rumor...DAMN!

Ya I remember it expiring a while from now. I'm glad I just took advantage of the sale when it started since I got my new console for only $50. 

" Ya I remember it expiring a while from now. I'm glad I just took advantage of the sale when it started since I got my new console for only $50.  "

it's okay, im selling my old one to a buddy of mine for 150, he didn't want to buy an Arcade version so it works out! 

Suck. Locals sold out day of release, plopped down $50 to reserve. I'm taking a guess that they'll screw me out of the trade in deal.

" @Afroman269 said:

" Ya I remember it expiring a while from now. I'm glad I just took advantage of the sale when it started since I got my new console for only $50.  "

Same here. Actually mine was like $65, but yeah, mad cheap. "

I'm still worried that GameStop stores will not be getting in enough 360 slims to meet all of these pre-orders, let alone satisfy consumer demand. Seeing them put the nix to this trade-in deal earlier than scheduled has only exacerbated my fears.  
 
Here's to hoping we don't see another Wii-like fiasco.  

I don't trade stuff in at Gamestop.  We have a Hastings Video Store that gives really good in store credit.  You usually get around $40 for a newer game.  I'm probably going to trade my HDD's, console, and 2 wireless controllers in on a slim there sometime in the next month.
 
Haven't played my xbox, other than Street Fighter, since I got my Wii though :)

I'm calling my local Gamestop where I have my pre-order in right now, and the dood just said that he hasn't heard anything of the sort about this.  He's calling the store manager right now to find out. 
 
....ANNNNND the Waco, TX Gamestop on Bosque Blvd. has just stated that they are offering the 360 trade-in deal until July 18th!!!  He also stated that the deal is no longer being ADVERTISED on their website...and that's all.
 
So I now question the validity of these articles.  Maybe some are doing it and some aren't?  I don't know.

I think it's ridiculous that stores other than Gamestop are being stocked with these new 360's in bulk while Gamestop is having a such a problem.  I went to Best Buy yesterday and they probably had around 40 of the new 360's in stock.

Wait, so some stores are still honoring the trade-in? I was going to go trade mine in last week but I couldn't find the offer on their site any more, then Google turned up a bunch of articles about that promotion being ended early so I figured that was that. Guess I'll call tomorrow and see if any local Gamestops are still doing it.

" I think it's ridiculous that stores other than Gamestop are being stocked with these new 360's in bulk while Gamestop is having a such a problem.  I went to Best Buy yesterday and they probably had around 40 of the new 360's in stock. "

" Wait, so some stores are still honoring the trade-in? I was going to go trade mine in last week but I couldn't find the offer on their site any more, then Google turned up a bunch of articles about that promotion being ended early so I figured that was that. Guess I'll call tomorrow and see if any local Gamestops are still doing it. "

I pre-ordered it a while ago because I was promised that they would still honor the trade in value when I came in to pick it up, even if the console came in after the deal was up. I hope that still holds true.

yep i traded mine in two and a half weeks ago because they said they would be able to get me a new one in a few days.  I still havent gotten one and am starting to get pissed off

i think they didn't think a lot of people would trade in their xbox's. i think that they should return the offer once they get more slims.

Shame that Gamestop just about never has enough of anything in stock. I was in a Best Buy just yesterday and they had a stack of the new Xbox's just chilling in the middle of their 360 area. Pretty sure they have a couple of those stacks in the back room as well.

What the hell? Just when I thought Gamestop had turned a new leaf, too. >.>