I've used Big Burrito for drop-off lunch catering a few times for 150-200 guests over the past few years.
They've been extremely reliable and the food was well received by my guests. I've mostly stuck with the entrees from Mad Mex. Setting up the orders and billing and communication have been very good. The deliveries have always been on time.
My orders have been burritos, salad, and chips and salsa. The burritos have been well built and the salads fresh.
I've also attended a few Big Burrito catered events with items from Kaya and Casbah as well. I've enjoyed the food they've provided. The cheese tables from Casbah are amazing.