it quite honestly depends. Ill tell you one thing though, the tier 7 and 8 pacts are high levels of rediculous, and the first few ones, like the research pact, and resoruce pact, and trade pact are great.
THe larger the map, the better the chances of pacts beig usefull. in, say a 2v2, if you and your ally dont have 5 planets each, then you polly should not be worried about pacts, however, if you each have 10 planets, they jut might be usefull.
in larger games, if your stuck in an econ spot... getting a supply pact to a front line fighter is gamechanging. (imagine going from 520 supply to 1420 supply without an increase in upkeep. ya. exactly.)... and if you can get away with it, is something you need to be going for very early on. (I mean, getting a trade pact and a metal pact with anyone is going to significantly increase your own income, and considering you are already in econ spot... if your in econ spot, going for the endgame civic techs, like RA, pervacive econ, and the pacts, is now definately worth it.
but, if you in a smaller map, pacts (and civic techs in general beyond tier 2) are generally not worth it, and you should be investing in fleet and such.
