I am in Israel as I write, staying in an apartment off the usual tourist route. iGo has been a godsend. It works quickly and accurately. This application has allowed us to travel widely in the country with confidence and without constantly refering to a map or a list of turns. Voice commands are clear. It works very well on my iPhone 4. We named ours "Shlomo" - as in "Shlomo says go left". Seriously, in the US I have been using NDrive for some time and it has been great. If I didnt already own that, I would not hesitate to purchase the US version of iGo.
That said, entering destinations of Hebrew addresses can take some getting used to, but the spoken english directions are excellent.