A definite sleeper hit!
I have seen on message boards and on various reviews that this game is easy, ridiculously so. I wouldn't necessarily disagree with that, but the setup with that many playable characters would require it to back off the difficulty in order to balance out the gameplay, and, while it is easier than most RPG's I have played on the DS, it is one of the more balanced ones out there. Sure, you can take a level-10 character and, especially towards the end of the game, they can get close to your strongest characters' levels within less than ten battles! I wasn't used to that, as if an underleveled character is waiting in the wings, you have to grind forever to level them up, so that was refreshing I didn't spend all day just leveling up lower-level characters. The story was good as well, and contrary to what others have stated before about your main Hero, I liked him as a character. It wasn't difficult to actually care about your main characters (e.g. friends of the hero), but the other 100 or so were mainly, for the most, collector's items in a manner of speaking. It was fun going out and finding some of these special characters via fetch quests, or story advancements, and this is one of the few games I enjoyed from the opening cutscene to the last, and I like how, on the ending, the game sums up what happens to each person who joined your company.
The graphics were nice, and the sound effects and music were excellent. I tend to pay attention to boss music in RPG's and this was better than most I've heard in any game, DS or otherwise. I didn't see much to whine about; some of the quests seemed to work against your characters, and I wasn't sure how to solve all of them (particularly one called "Minen's Background"), and during battles with some larger enemies, you couldn't always see the damage your party was dealing to those enemies because the camera would fix in front of your party instead of behind like it tends to do; but outside of that, this was minor and didn't really detract from the adventure as a whole.
Suikoden: Tierkreis did what few RPGs have done over the last few years; and that was surprise me. If you like portable RPGs, you must try this one out; you won't be disappointed.