Today I tested Gmail with my user agent spoofing Android Chrome and I got a much better experience than the HTML version or the Desktop version (which you can get by spoofing Firefox’s UA).
Using WebIDE, set general.useragent.override.mail.google.com to Mozilla/5.0 (Linux; Android 4.0.4;) AppleWebKit/535.19 (KHTML, like Gecko) Chrome/18.0.1025.133 Mobile Safari/535.19 or similar and Gmail works well.