ZeroCater is great! We have used them a few times and been impressed with the quality and variety. My only complaint would be that take-out food can be greasy and unhealthy sometimes. It'd be great if ZeroCater could cater to the "healthnut" crowd.
My company usually has healthy, seasonal lunches cooked by an in-house chef, but when she is not available we use ZeroCater. The discrepancy between healthy home-cooked food and sort-of health catered food is more visible when switching back and forth.
That said, the ZeroCater guys are great and I'm quite impressed with the service. If your startup isn't eating together yet, you should. It's definitely worth the cost!