This is just completely unfounded. Not sure how to respond to that.
The gateway/configuration is web-based, but the clients and designer aren't, so this isn't relevant.
See above. The clients and designer are native applications; they aren't slow and aren't run in the browser.
Many people are confused by the 'web-launched' terminology. All it means is that our native client/designer apps can be launched from a central webpage (the Ignition gateway), and don't need to be installed at every workstation manually.
Not sure what to tell you about that 
Other people are welcome to step in with their experiences.