Barely great game.
It's very much stylistically similar to Final Fantasy Tactics with a few interesting tweaks such as Fusion - combining two items to make 1 unique item (think bow + axe = cloth shirt?)and much more in-depth character development.
What I really liked about Stella Deus was its unique twist on turned based combat - the ability to speed up a characters next turn by taking no action or little action. Stella Deus brings the same kind of strategic depth by also utilizing the same feature.
Another important point to make is that so far i've found Stella Deus to be one of the more difficult tactical RPGs I've ever played. Despite spending a fair amount of time leveling up i've had to resort to cheap tactics in a few battles. (such as getting a boss to chase one character while pummeling him with arrows for an hour from an elevated position)This does a lot to hurt the overall experience.
In short there are a lot of other tactical RPGs for the PS2 i would recommend over Stella Deus (such as Disgaea: Hour of Darkness and Growlanser Generations), but if you especially liked Hoshigami or want something a little different then Stella Deus is definitely worth checking out.
Granted it's not FFT yet it's the best Strategy RPG out there right now. the gameplay is just fun, the graphics and the art design are pretty smooth and accomplish well on getting the player in the feeling of the game. The story is not as complex as FFt but its still pretty good, being far more serious than that of games like Disgaea.