with new system escrow , how dispenser ( or steam trade system,)can sell games untradables? imagine
guy added you and buy one game untradable for 3 keys,he pay with keys and have escrow 3 days, you send game and guy cancel trade,steam dont have support in gifts untradables ,i think is a problem

When trading via steam you simply only send gift after you receive keys, means after 3 days. If you trust the buyer, you can send right away, but to be on the safe side, just wait for keys to be delivered after 3 days.

According to statement from Joto, the users with escrow won't be able to use dispenser service, so the problem you are describing won't happen.

I understand that handling escrow trades and cancelations brings some implementation overhead, but ideally, i would like to see something that other trading sites implemented as well (steamcardexchange, etc.) meaning, the user deposits keys and gets credits 3 days later after the trade offer went through.

For old style trades, there could be setting, something like "Allow escrow trades", turned off by default and the bot owner could enable it if he is OK with having his games put on hold and either being "frozen" or getting taken out of trade completely. The cancelation would need to be handled then by dispenser and the items put back into the trade, but it's a hassle to implement i guess, especially since old trade style maintenance and development are rather passive now. (Maybe the same code could be used, that kicks in currently when someone sends trade offer for a gift, but instead of blocking it for 3 minutes, the gift is blocked for 3 days until the trade offer went through)

I think I saw somewhere Joto mentioning that for the moment, only guys with mobile authentication activated on their steam accounts will be allowed to trade on dispenser to smooth things out. Not sure about it though.

additional problem is that you may need check your history for many pages (if you trade direct with buyer). For example, you made trade at 15 december and you both need to wait untill 18th. But all all trades you'll make between 15-18 would be early in history. So at 18 you may need switch couple of pages to figure that exchange completed and not canceled by other side.

I need check mail then

Well, the steam app is not just for windows phones, it can run on android ones as well. Although, yes I do agree with you that the system proposed is unfair, & untradable gifts for only credits would be a good idea instead. But for tradable gifts, I think mobile authentication is really the way to go, for smooth working.