I received my invitation to Sling TV and signed up last night for the 7 day free trial. I can't confirm you need a US credit card and address (though the address field does not have a place for country) but I have both used them.

Applications exist for Windows, IOS and Android and I tested Windows and Android.

Not sure what display technology they use for Windows (I was using Windows 8.1) but it's not in a browser but a specific application. Using Unotelly the content streamed fine but the choice is limited, being only ESPN, ESPN2, TNT, tbs, Food, HGTV, CNN, Cartoon and some Spanish language channels.

Ads appear on the TNT, TBS and Food channels but from what I have read they are not necessarily the OTA ads but ads perhaps tailored to the streaming market. On ESPN during ad breaks you just get an ESPN logo saying ad break.

I tried the Android app on my N5 and a N7 and it worked fine, streaming in good quality over my WiFi.

No way for me to watch on my TV yet. A Roku device is supported but my Roku is connected to my projector. Also I think the Amazon Fire and Stick are supported so that might be an option. Also no   Chromecast support either. I tied to sideload the app on my Google TV box but it came up with a package error so I don't know if it's the platform or the way I got the apk to the device. I couldn't find it in the Play Store.

I was hoping to cut the cable here (VF cable) and stick to Freeview and this but there isn't enough content yet.

So after the 7 days trial I am going to cancel. It was nice to get ESPN though but many of the games shown on ESPN international (e.g. Superbowl) might not be shown on ESPN US since local networks would have the broadcast rights. But the rest of the content is not so interesting.