Awesome Ego: Material-D aka Lord Dearche. Figures, since she is a bizzaro version of the soft-spoken and humble Hayate. And her ego became more awesome in G.o.D.
Ensemble Darkhorse: The Materials were really minor characters despite being the main villains in this game. However, they were popular enough to appear again in the next game, where their personalities have been fleshed out and their backstory is expanded. They have become even more popular, gaining their own spin-off manganote Magical Girl Lyrical Nanoha A's Portable: The Gears of Destiny - Material Musume and appearing as major characers in Magical Girl Lyrical Nanoha INNOCENT.
Hilarious in Hindsight: Material-L is a Palette Swap of Fate in this game, however, if you've ever played Magical Battle Arena, you'll remember that some stages in both the story mode and the survival mode have palette swaps of the characters as well, and one of Fate's swaps? The hair color is blue.
Jerkass Woobie: Some of the Dark Pieces, especially the Dark Pieces of Vita (with the one exception in Zafira's route).
Even Better Sequel: Eleven more characters, even ones from otherseasons, a better, long story instead of nine character routes, better animation, fluid battles, more clear sound quality, developded gameplay, more modi, better voice acting, and the Characterization Marches On for the Materials.
Einhart is the most broken character. Her skills contains long range counter that is very quick to the point that it's next to impossible to dodge by the opponent, and a skill that makes her invincible for a short amount of time, she can still attack her opponent while in this state. Heck she and Zafira are the easiest to use against the SNK boss in the first round.
Chrono's Blaze Cannon isn't particularly strong and has rather short range, but it's one of the quickest long range spells to use, making it easier to destroy U-D's Super Armor quickly.
Nanoha, the White Devil herself. While not particularly strong in close range, she's not that bad either and has very simple, but effective combos in that range. In long range, however, she's probably the best character there. Her uncharged Divine Buster is very quick, but still strong and has a excellent range, and the charged version is even stronger. Her Accel Shooter are homing bullets, and she can bind the opponents with Restrict Lock while they are blocking. Her Limit Break has a good range and its power is a little above average. And then we have her Full Drive exclusive move, the Hyperion Smasher. Its charge time is long, but the energy is protecting Nanoha while it charges, so if you don't attack her from other directions than straight forward, you cannot stop her, unless it is U-D's Vesper Ring. And the damage is massive. Also, Nanoha's defense is average, so she's not a Glass Cannon. In the second round against U-D, Nanoha is the easiest one to use because you don't have to be afraid of U-D's long range moves with Nanoha's quick Divine Buster.
Yuuno's shield charge Protection Smash. Get used to seeing it if you're playing against anyone familiar with his more damaging combos.
Basically all of U-D's attacks in the later parts of the story can count. Particularly:
Her Beam Spam. Not only she fires dozens of magical balls, they do a lot of damage. Risking a Guard Crash is one of the better options rather than dodging (unless you are at a long-enough-range to move aside). If you are close enough to her, you can actually rush up and throw her since the move's charge time is long. And of course, anyone playing a character with a Catch and Return move will actually want the AI to abuse the Beam Spam move.
Her grab move has a ridiculous cheap range.
Her counter attack works not only in close range, but in long range, too (if you're close enough to her). And the counter is basically a middle range attack.
That One Level: Sequence 6, the one with Chrono and the Liese Twins. Bad enough that you're forced to play with these rather hard to use characters, but you must also fight against opponents who had just gotten their Mid Season Upgrades and are thus stronger and tougher than usual. Oh, and you need to finish this sequence to unlock the Liese Twins outside of story mode, so no getting used to them in training mode for you.
They Changed It, Now It Sucks: When the official names for the Materials were revealed, there was RAEG. The fact they misspelled Material-D's name as "Load" Dearche was pretty hilarious though.
They Wasted a Perfectly Good Character: Actually costume. Some fans are disappointed that Vivio can't use her Sankt Kaiser Form as an alternate costume, despite it appears in the Story Mode. The costume can only be accessed through a PSP hack code as shown here.
Tier-Induced Scrappy: Shamal is still pretty weak, the Liese Twins are also weak, and Chrono too. It's made worse by the fact that you are forced to use the characters to continue the story. Not to mention that even Yuuno has better offense than those characters, and he's the Stone Wall of the group.
Some players have problems with playing Shamal and Chrono against U-D in the first round of the final battle. Especially the latter. However, Chrono actually is one of the easiest ones to play against U-D. His Blaze Cannon doesn't make much damage and has a rather short range, but it's one of the quickest long range attacks in this game, which makes it actually quicker to destroy U-D's Super Armor. And U-D is easier to defeat in close range combat anyway.
Surprisingly enough, Shamal is one of the easier characters to use in Time Attack Mode.
Fate in Sequence 3 (especially if you play Arf against Presea) and later in Sequence 7-R.
Professor Granz Florian. A Nice Guy who just wants to save his homeworld instead of leaving it, but he makes little to no progression. In the end, he dies from overworking before he could see how his works eventually pay off.