Builds off of the best parts of previous RTS games and in the end creates a complex and compelling experience.
The best part of the upgrade interface is it feeds directly into the pace of the game. The action continues even as you decide what path to take your Demigod. This may seem frustrating or overwhelming at the beginning, but once you settle into the game (about the 2 hour mark for me) you quickly learn the paths that best suit your style of playing. In addition to abilities and spells, you can also upgrade and customize your Demigod with a series of items from the Item shop, as well as Favor items, earned through the course of battle. All of these features are unique to the 8 Demigod's you pick from - so the options seem endless.
This game captures the essence of all RTS that have come before it, minus the stale and routine build-up phase in the first 20 minutes of the skirmish. No peons to order around, no building tree's to learn, just straight out battles.
I would recommend this game to anyone looking for a fast paced, moderately complex, start it up and kill type of game.