Client already produces (most of?) the needed information summary, at least at folder level. I'd suggest detailing it to file type level.

What I'd like to see, when I mouseover a username in a channel, is:

Audio:  345 GiB in 12345 files
Video:  2.1 TiB, 4321 Files
Images:  12.3 GiB (98765 Files)
Text:  32.1 M Files (8.9 TiB)
Other: 56.7 GiB (345 K Files)

This small packet if info can be transferred without all the overhead of browsing a user and might inspire browsing.

Also, an abbreviated total of summary can be added to the username list also (ala Tixati), while for fopnu it would be file count and total shared size. Perhaps user option to enable display of each alongside the user's name would be the way to go.

I have reservations regarding this type of feature simply because we have seen how similar features have been utilised before to trap sharers of large quantities of files, not on this network of course but the ability to hunt down the "fat fish" by sending out a few packets and storing the results on a per user basis does allow the anti-p2p folks a leg up, in general the most helpful anti-data-mining trick is to allow only browsing etc of users in the same chat room or from a previous transfer transaction and strictly disallow browsing of search results until then.

A summary could also be made available at that point in time using a simple tooltip "mouse over" effect, if the users where allowed to enable/disable this feature at both clients that would suit nearly all folks as you would then be allowing the activity or not as your choice and also allow the programmer to set the client to grab the extra data for those with the option set affirmitavely.
Of course the same method could be utilised for the browse..lol.

My suggestion was related to browsing what a user shares in a channel, which is then semi-public. It would not reveal any stats on how many or what types of files a user may be sharing in other channels or private groups.

In tixati, a few users offer to share links in chatrooms and an indicator is provided to show just which users are worth browsing. No sense browsing a user without any visible shares.

That's basically all I would ask for as I too greatly appreciate the ability to limits select shares to a select group or person.