Just last week I purchased the SkyRadar L and a new iFly 720, and I also have an iFly 700 (now surplus). The SkyRadar worked fine with the 700; but I wanted a wireless connection instead of USB so I bought the 720. I had also connected a borrowed SkyRadar S to the 700 and they worked fine together. When it came to purchasing an ADS-B receiver, price was the main factor and SkyRadar had a 20% off/free shipping deal.
On the SkyRadar, I have a small 12v battery just for it, & I power it up during preflight and power it down on arrival. As for the lights: my power light also blinks slowly. The GPS light stays solid when locked onto the sats, and I've only seen the ADS-B light blink "on" a few times. When flying through Mississippi where there's no ADS-B coverage, the iFly alerts me if it has not received data from the SkyRadar in more than 66 seconds. Also, by looking in the "About"/"Connected devices" page of the iFly, you can see how many TAF's, Winds Aloft, RADAR, etc. reports the iFly has received from the SkyRadar. It's quite a large number!
I'm very happy with the SkyRadar and the iFly combination. It definitely makes me a better (informed) pilot.