Likelihood Bob the Tomato's Coffee Shop is collecting your info: Low.
Airport itself? Low Other people in the airport? High
It's not necessarily the place itself, but anywhere there's open (or easy to get) WiFi, the chance of nefarious users increases dramatically.
Citation needed. I get that it's trivial to actually do, but do you have any studies that show that a lot/any WiFi is being sniffed and/or MiTM'd? The most I've seen is airports and so on tracking people via MAC addresses or the WiFi AP names they request.
Android phones are sold globally, remember. There are much worse places to "moor your ship", data-wise, than the US. If this VPN circumvents Chinese Internet censorship, for example, then it's a win by sheer numbers, whatever it does to US domestic citizens.
Honestly, how are everyone's alarms not going off right now? Google fiber, alright, at least I get fucking 1 gbps. Google VPN?? A VPN?? Keep Google/<substitute-3-letter-agency-of-the-day> in charge of what you use to hide your illegal torrents?? Genius.
Are you torrenting, or planning terrorist acts, or whatever else, on your mobile connection? You're crazy. I would never do anything I'd want to hide from the government on my phone; it's already got that mysterious baseband coprocessor running god-knows-what with direct DMA access to main memory. Adding a VPN pipe directly to the manufacturer doesn't make me any more potentially-spied-on than I already was, since the ISP already, effectively, had arbitrary code execution and their own backchannel.
Security professionals don't avoid smartphones altogether, of course; they just use them only as conveniences for "unclassified" day-to-day operations.
That's the logic that brought us ads plastered all across the web, with nothing sanctified, including the _content_ of the web page. 'I mean, we _already_ see them anyway, what's the difference if they're blinking/videos/popups? I mean, we don't have to look.'
And yes, I pretty much use my mobile as less as I can, just for these reasons. I'd never use it willingly as long as there's even a trace of google in android. However, can you elaborate more on the coprocessor? Maybe some additional reading? I'm very interested in what possible surveillance do they have in the hardware itself.
P.S - At this point, I'd rather use apple than google. At least apple can't tie my activities to my search results, which is an insanity that the world will come to terms with several years down the road, and then repent.
It's hard not to see an offer of at least some form of security to be a net positive in that case.
If they don't provide an easy and apparent way to turn that off, this is the word that always sets off alarm bells in my head.