Soldato
To be fair, I don't think I tried Netflix. I seem to recall Prime Video playing in an odd zoomed in aspect ratio and not being anywhere near as stable as it is on the Fire TV. That said, I also had a lot of issues with Plex and I did a factory reset on the Shield and since then Plex has been absolutely fine, even with 30GB+ BD rips. I'll give Prime Video and Netflix another go.
Definitely give them another go. I've never had any issues like that. My experience with the Shield is absolutely 100% spot on, certainly with the four things I use it for: Plex, Youtube, Netflix, Prime Video