Ed, Rich, Calder, Sean, and I have played team games before. There wasn't much laid out for us we pretty much just took our normal 35pt lists and played until one caster died. We also allowed our team mate to count as friendly but not FF (I think that's what we came to) unless we were both same faction.
Yeah, some whacky shit happened on both sides... But nothing over the top. Like most things, the balance is both teams can break stuff.
I felt like these games worked well enough. Scenario I feel might be a clusterfuck though, and the fact that only one person had to die really made you work as a team so neither person lost. Plus the points didnt feel all that bad... Ed and I had fairly heavy infantry lists (eGaspy + Ashlynn) and other than a few occasions where models stepped in toes it was fine. Also it was a blast for people to get spells and buffs their faction never had access to (maybe an iron fleshed bane knight, or quickened forge guard?) some real fun can be had. 25/35 is fine. 35 worked and would be great if any of us sat down and worked on lists together.
Just some casual but real world experiences.