Game Completion: Currently on Chapter 4-5. About 88% complete, I think.
I really want to write about the plot of the game in depth, but I really should wait until I compete the game. So, more gameplay stuff.
Classes: I have mixed opinions on the new three-tier class system used in Radiant Dawn, a significant change from the two-tier class system from the earlier iterations of the series. I think it has a lot of good qualities, but at the same time, the implementation of the idea is a bit uneven.
Even though the addition of a whole tier is a big change to the system, in practice it actually doesn't change the feel of the game very much from earlier iterations, because the majority of the characters start at the second tier. The few characters in first tier classes end up behaving like the three journeyman characters from Fire Emblem: The Sacred Stones, characters who start weaker than normal but end up very powerful (well, some just stay weak in this game). The characters only reach the third tier late in the game, like normal promotion in older Fire Emblem games. However, it lacks the advantage from The Sacred Stones of letting low-tier characters be more flexible than more advanced characters. Also, the very large number of levels each character needs to gain in order to class up exaggerates differences in stat growth, but more importantly, it severely limits the usefulness of characters who are not available for many missions (like the Crimean Royal Knights). Because of this, having more tiers of classes may not be a good match for a game with shifting perspectives.
Another issue with the three tiers of classes is that the benefits from classing up are uneven between the different classes. For example, Falcoknights and Dragonmasters (second tier classes) have access to two weapons, but similar Paladins don't get a second weapon until the third-tier upgrade (when they already have less mobility and lower stats). Many classes don't get the classic benefits of classing up (like sages acquiring staves) until the second class up, while others gain such benefits at the first class up (everyone gets more movement, Swordmasters get improved critical hit rates, etc), and other classes get powerful, unheard of abilities at second class-up (like Marksmen getting improved range for bows).
Still, one of the more interesting things about this system is that it lets the controllable characters rise far above normal enemies. Enemy grunts don't have access to third-tier classes (instead, they just get higher stat caps), so they lack the special abilities, powerful attack skills, and impressive appearance of classed-up characters. It lets fun and deadly attack skills like Sol, Luna, and Astra be available to every character, but keeps them away from enemy grunts, who would easily kill a controllable character with just a little luck with such moves (which would be overly frustrating). Also, it matches a lot of the tone of the story of the game in Part 4.
Weapons: I really don't have much to say about the classic weapon triangle of Fire Emblem (Axes, Swords, and Lances). Those three weapons have a lot of variety and work well in this game. Similarly, I don't have a lot to say about the Anima spells (Fire, Wind, and Thunder), other than that they should probably have at least one spell in each category which does something unique, to differentiate the spell types a bit more than they are. Also, the fact that the mission I am currently in, very late in the game, is the first chance to exploit the special advantages of the Fire spells (bonus damage to Beast Laguz), and Wind spells are barely any better, is something of a flaw in the game.
I think that Light magic and Dark magic could have been handled better in this game. As a whole, neither type of magic has any special property that would make it unique compared to Anima magic. The main benefit of Light magic, its effectiveness against Dark magic, is limited by the severe lack of Dark magic users in the game. Obviously, that lack hurts Dark magic as weapon type as well. As a whole, having two Trinities of Magic has diluted the purpose of these spell types too much, and it might be better if the Fire Emblem series returned to the Fire Emblem 4 system of having both Light and Dark be effective against the Anima types, and neutral against each other.
Bows suffer a bit in this game from the prevalence of good weapons from the main Triangle which have a range of 1-2. This dilutes the niche bows traditionally have had in the series (being the main ranged physical weapon) significantly. Also, the very low accuracy and rarity of longbows with a range of 2-3 removes an advantage. However, the ability of the Marksman class to use all bows effectively at a range of 2-3 restores that advantage, just a bit too late. As a whole, I think the advantage of bows with a range of 2-3 should be maintained more consistently across the game. Otherwise, bows work well.
I think, as it stands, Knives are not really in the same category as other weapons. They still show too many signs of their very recent evolution from thieves using swords. The stats for the silver dagger are nearly identical to the stats for a silver sword, and the only classes to use knives are the rogue variants. It would be better If more classes used them (Archers, maybe?), and they were further differentiated from swords.
Crossbows are actually one of the best innovations in the weapon system of this game. They work well, and feel more distinct from bows than daggers are from swords. Still, it would be better if more classes had access to crossbows, if there was a bit more variety to them, and if they were actually ranked like other weapons. Most importantly, it should be clearer which classes could equip crossbows (since this information is not available on any character information screen in-game).
Finally, I think the whole system of building up weapon levels is a bit flawed. Currently, there are too many ranks (E through SS, making each growth of weapon level mean too little), a class needs to be in at least rank C to even use decent weapons of a category (so even third-tier Marshalls need to equip weak Iron Lances), and physical weapons and magic categories seem to build up at radically different speeds (causing mages to fall far behind). Overall, this system just overly restricts characters from accessing the rare and powerful weapons of the late game (not fun), and has no clear benefit. It would be better to revert to the much older system of having weapon levels build up automatically at class-up, with certain characters having bonuses to certain weapon types.