I will most likely buy the new Koren siddur some time soon and while I think it's great that there are PRAYERS for Israel included, I'm still waiting for a Hebrew-English siddur to come out FOR Israel.
Have I lost you yet?
As my husband and I discovered at the Brit of our first son, some things are different when you're in Israel. Like what is said at the Brit. Oh sure, the Brachot are the same but there are several key Piyutim the father needs to say that differs from Israel and the US (and most likely all of Chu'L). Now for someone who can read Hebrew well, that's not an issue. But say the father can't spot-read Hebrew and has been practicing his part from his Artscroll siddur for the past month (because he knew his wife was having a boy) and then is told at the Brit that what he just started saying is wrong. Now faced with having to read unfamiliar Hebrew, he's thrown into a panic and simply forgets pretty much everything he's spent a month learning... Brachot and all.
Needless to say when we found out I was pregnant with our second son I bought him a Hebrew siddur for Israel (happens to have been a Koren edition) so he could learn what needed to be said.
I'm sure there are other things, some more minor than others, that are different.
I also wouldn't mind a Hebrew-English Shloshet Regalim Machzor for Israel either... cut out all that 'second day' stuff...