Do you have any advice regarding Birthright Israel?

I’m asking those who have been on Birthright, or know something about it, not generic travel advice. I’m looking for advice about which season to go in, what organization to go with, and one other issue (see below).

I heard it’s not that cold in the winter, except in Jerusalem. Confirm or deny, anyone?

A few other details: I would consider myself reform, but I do enjoy many aspects of the conservative movement, such as slightly more hebrew being incorporated into services, and prayers being said more frequently.

Other issue: I have a friend (actually an exboyfriend, that i’m still friends with) who is also planning to go soon, and we’ve discussed going together.
Advantages: having someone I know, being able to share the memories with someone from my hometown, who I know I’ll still be friends with afterward, he’s an interesting person, and it would be cool to hang out with him
Disadvantages: he is my ex, and i might get annoyed with him really quickly, my sweetie pie would probably worry about me more than if i was there by myself, i might not meet as many new people (but i’m not that social anyway, so i might just keep to myself, who knows), he is pretty secular, so it sounds like he wants to go on a less religious kind of trip than i do.

also, anything else you can share would be very welcome—how much to pack, which sites were your favorite, what you liked most about your organization’s trip, etc