I have both of these phones and I was wondering if Blackberry messenger can be used on the samsung eternity? There is a section in the Eternity for Blackberry files/applications (can't remember off hand which) It would be sweet to be able to use messenger with both.
Sorry, I don't think that's possible with the Eternity. I know there's BB Connect, but I think it's only for Windows Mobile, Palm and Symbian smartphones.
My wife has an eternity- there are a few IM clients pre-installed (AOL, Yahoo, Windows live, I think). What I don't know is if they use SMS to send messages; probably a question AT&T could answer.
There are any number of other IM clients you could use on Blackberry that can connect with the above mentioned IM services.