> since their uptime way beats ours

You link to Google's JS so your users can still get it when your own site is down?

If you hosted it yourself your users would see a working site whenever you were up. Now they will see a working site whenever both you and Google are up. This has not improved effective uptime for anyone. (On the other hand, Google might serve the JS faster, especially if your users cache it. They may also keep their copies more up to date.)

GP's point is that it also hasn't noticeably decreased uptime. So especially if there's a speed benefit, why switch?

Ahhh! See, we didn't realise that at that moment. Thank you :-)