Ring's professional monitoring isthrough Rapid Response Monitoring Services, and it's one of the more affordable services available. For $10 a month (or $100 a year if paid up front), you get the benefits of dispatchers on standby, and this includes video storage for any Ring cameras you might have. There's no long-term contract, either, so you can cancel any time you don't need it through the Ring website.
All that said, the biggest flaw with price is that purchasing Nest’s multi-purpose sensors may be forcing you to purchase more equipment than you need. Most homes don’t need three motion sensors, especially if the sensors have a decent range. Remember, Nest’s motion detectors only detect movement within a 10-foot range, the abode motion sensor has a 120° field of view and can detect motion within a 34-foot range so you would need at least two Nest motion-enabled devices for every one abode motion sensor. Ring’s motion sensor’s range is unlisted, but I tested it at 35 feet, and it worked perfectly.
It doesn't work with the Amazon Cloud Cam indoor home security camera, either. Here's what a Ring spokesperson had to say about it: "Ring Alarm does not work with Amazon Cloud Cam at this time. While I can't comment on the roadmap at this time, what I can tell you is that we will make product decisions based on what will best empower Neighbors with an affordable, effective way to monitor their homes."

UPDATE: 1 Year-On. We have had the Ring Pro for One full year now. I've also added two of the chime accessories. I'm just as happy with it now as I was when I wrote this review. We tried to trouble shoot the sound a few times and still have had no luck with it. I think my unit might just be defective in that area. However I still think if this was advertised as a camera only, it would be 100% worth the price and 5 stars. I did have someone point out the sticker over the ring might be the cause of our sound problem, removing it didn't help.
Great article with lots of useful information. Very comprehensive comparison that really helps people make a wise decision based on their particular needs. FYI, I chose abode for my home security needs because it’s a proven shipping product and it integrates well with other systems. Although the camera quality might not be as good as others, it will suffice for my needs.
The most useful product offered by Nest that the Ring system does not have is a connected lock. This tamper‑proof, key‑free deadbolt connects to the Nest app, letting you lock and unlock your door remotely. Users can also create passcodes for family, guests and people they trust, or give them a Nest Tag programmed to let them in only at certain times of the day.
This is the Spotlight Cam’s bigger, badder older brother. Equipped with two ultra-bright floodlights and a siren, the Floodlight Cam is impressive enough to scare away any potential intruders who approach your home. However, its extra power means it must be hardwired to weatherproof electrical boxes, an installation process that may limit where you’re able to set it up. However, if you want to feel secure and safe at all hours of the day, it might be worth the extra effort.

Update 1/24/16 - I have found a fantastic use for the Ring Doorbell and Chime. My mother-in-law, now in her 90s, lives by herself. She has become hard-of-hearing and often does not hear the doorbell. By installing the Ring on her door, she now is bothered much less (solicitors tend to recognize it and don't seem to like it) and when someone rings the bell, the Chime, placed by her favorite chair, gives her a better chance of hearing someone at the door.
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