I've reviewed CZ twice before but given recent changes, here is an update.
Casa Zen remains a standout option among all others in Santa Theresa. Room rates (private or shared) remain very good and the atmosphere is hard to beat. As many other visitors have noted it is generally a very chill space attracting a variety of individual, couple, and group travelers from all over the globe.
The major change to CZ since last year is that the restaurant has closed. The upside of this is that the former restaurant kitchen is now open to use by all visitors from 8am to 8pm, providing a much improved situation for those on a budget who wish to cook for themselves. Another side-effect of this is, the evenings at Casa Zen are even more chilled out than they were before, since there are no groups coming in at night for dinner -- the separate dining room (rancho) is effectively dedicated to guests now as well. For those lamenting the closure of the restaurant, nearby Casa Del Mar (25m away) has expanded its kitchen and restaurant (including a wood fired oven) with a bar to offer a stumbling-distance option for drinks and dinner.
If you're a surfer like me and want access to your breakfast/pre-surf chow, stick it in the old communal kitchen fridge, so you can get at it before dawn-patrol surfs, which are typically the best conditions here. And when you get back from that early morning surf, the complimentary breakfast will be there waiting for you.
CZ remains exceptionally well staffed and tended. The (numerous) shared bathrooms and showers are cleaned daily. Your room will have its linens changed and be swept out occasionally during an extended stay, but if you want it done more frequently, just ask. I found twice per week to be fine.
They continue to offer laundry service, board rental (beginner gear), and bike loan/rental.
Don't forget to sign the guest book!