Power Tree System: All classes possess 8 power trees: a class-specific power, five additional powers, a class-specific passive skill, and Fitness. 21 points are required to max out a power. Shepard gains 2 skill points per level up (e.g. a Lvl 10 character will possess 20 total skill points to distribute). Assuming this remains static up to Lvl 60 and that no other means exist for acquiring more skill points, a Lvl 60 character will have 120 skill points available. Therefore, Shepard will be able to max out 5 separate powers at most.
Squad Members: Squad members have only 5 power trees: four powers and a class-specific passive skill. They gain 1 skill point per level. All squad members level with Shepard. Assuming this remains constant to Lvl 60 and no other means exist for acquiring more skill points, a Lvl 60 squad member will have 60 skill points available. A squad member can thus max out 2 separate powers at most.
Note that the displayed information for power stats is auto-updated based on the effects of other skills. Example: A power inflicts 100 DMG at Rank 1. You then upgrade a different skill that has the result of boosting all other power damage by 10%. The description for the first power will change to show it inflicting 110 DMG at Rank 1.
Cooldowns - Cooldowns are affected not only by upgrades to that particular power, but how much weight Shepard is carrying (eg how many guns). For example, a player with a completely un-upgraded power at Rank 1 but only carrying a pistol will still have a much faster recharge time than a player with the same power fully upgraded, but loaded down with many weapons.