how important are letters of rec in rush?

People will tell you recs aren't important. But they have probably never worked behind the scenes during rush. Recs absolutely do help. They won't make or break you, but in most houses they may guarantee you an invite to round 2.

Recs will also help a house when they have to make a difficult decision between two girls who they like equally. If one girl has a rec and the other doesn't, guess who gets invited back to the next round?

Recs also will help the sororities get to know you better. When you rush, it's not an interview. So you may not get a chance to tell them about all your accomplishments and other cool facts that might make you a more appealing PNM. If you end up just chatting about casual things, they won't leave the conversation knowing much about you. Sure, they can check the resume that you submitted online when you signed up for recruitment, but sororities find it MUCH more trustworthy to get all that information from an alumni, because for all they know you could be lying.

When a sorority knows more about you, they'll be able to better match you with a girl in the house you have stuff in common with. When you talk to a girl who you have a lot in common with, she's much more likely to like you and thus give you a higher score/ranking.

Recs also show a sorority you are interested in them. It shows you were willing to put in the effort to get them.

Sure, we're not at Alabama where recs are REQUIRED, but they sure help a LOT more than people realize.

Get them if you can. They definitely help.