Well, I do use GPE with GCal sync myself too. But its more of my persoanal calendar.

For collaborative calendering I always fire up the online version and starightaway enter the evenst I want to share in my friends calendar. GPE seems only to work wiith the default Google calendar and not with the other ones (I use 3 Gcalendars in all).

30Boxes I use also more as a aggregator of my friends stuff apart from the calendar also. Sorry, but GPE does not integrate here. Plus I subscribe to my google calendar in 30B also.

And in these cases where the content is rather large, I do like having the streamlined (to whatever degree on the Nokia N810) iPhone versions so that it loads and shows up faster over 3G connections. Also I like to see it fit the page rather than have to scroll too much.

The only reason I have to search and use the iPhone version URL's is because I don't want to change my browser useragent each time I want to switch back and forth between iPhone / mobile versions and normal full functional browser versions for other sites.