In other words, the gmail style view is a killer feature for some people, so if roundcube can offer it as a choice that would be great from my point of view. Traditional threading is also a nice choice and it would be great if they could both be integrated.
Well,
I guess that one should check whether google has a patent for this kind of
viewing mails. I don't know, but I'd say you should check this before
starting to implement it...
Just my few cents,
Greetings.