Other than the meat issue, can one rely on the various Rabbanut hecksherim in Israel? I was told they rely on the most meikal of heterim.

As I have written in similar questions, what the Rabbanut gives a Hechsher for is kosher. The Rabbanut hechsherim are to ensure that klal yisrael is eating kosher even those Jews who may not give eating kosher a second thought. We therefore owe great gratitude to the Rabbanut that most food establishments and products in Israel are kosher and that presenting non-kosher food items as kosher is punishable by law. Unlike abroad where in many places it is difficult to find kosher food, fortunately in Israel it is difficult to find non-kosher. This applies to meat, fruits and vegetables and any other food product. However, in order to ensure that klal Yisrael is eating kosher, the Rabbanut does not always follow the most stringent opinions in Halacha. Therefore, if you choose to take upon yourself more stringent observance or what is labeled as "mehadrin", it is your prerogative. However, any stringent observance does not diminish the basis of the Hechsherim of the Rabbanut.