I worked in an Agile house for 4 years.... and went to local Agile meetups regularly. Overall, my opinion about Agile is bit.. hmmm.. Fragile!
Firstly, Agile is good at getting half-baked products out of the door. Two (2) week cadences, where features to be build, demo and shipped is quite narrow... and you get time to barely test it. Yes, you can demo it is working, but it is the tip of the ice berg. How the feature interact with other features or infrastructure is the iceberg what's below the water surface.
Secondly, Agile is good at sweeping hard work under the carpet. For an example, because there is no centralised architectural thinking or planning, every developer goes wild and build their own architectures... half of them are duplicates doing similar functions (and not to forget, poorly tested). Things like database or API designs generally takes lot of planning and thought process. By design, Agile doesn't allow such lengthy ventures.
Thirdly, Agile not scalable. Agile works best for smaller website projects.. say 5-6 page dynamic websites. If you are to do a huge mission critical project involving 100+ templates, 20+ devs so on... Agile will fail half way point, and you will have to downgrade to Waterfall, and pretend you are doing Agile to your client... which method I christened as "ScrumFall" (after James Bond movie).
Overall, I promote "prototype, maturity and ship" model (I don't know there is an actual name for this). Basically, try out prototypes first.. if it works, then promote to regular development, and finally production. I see JavaScript & C++ language committees adopting a similar work cycle. Overall, they are doing pretty well IMO, with regular releases and good quality.