Gut Responses to the classes as that is as far as I have read.
Beguiler: About time they did this class. Frankly I like these type of classes,(Dread Necromancer, Warmage, now the Beguiler) better than specialist wizards. It would seem most new caster classes can wear light armor and have d6 hit points. I would safely say in any newer version of the game, d4 hit points are going away. I liked the idea of this class and most of its execution. I wish it had a conceal casting type power, as that seems very applicable to a illusion/enchantment caster, and I still feel it was modled too closely on the Warmage, but a good attempt. Overall I think it would be a fun class to play for someone wanting to play the consumate charming one step ahead
enchanter, definetely a finesse character, though with Use Magic Device and taking Shadow Magic as an advanced learning spell, some brute work can be done.
Dragon Shaman: D10 HP, 3/4 bab. Cleric saves. Simple weapons, medium armor. Pick a Dragon Color, get bonus skills,
get free Skill Focus feats in bonus skills. Get Auras to boost your friends. Get Breath Weapon, Get Natural Armor bonus, get wings at 20th level. Get a healing abillity at 6th level, that despite what the fluff description says , will not let you heal like a cleric. Mechanically, the class works, but it doesnt feel like a Shaman or
say a Totem Warrior from AE. I cant say it is the most creative class.
Duskblade: First off hate the name. Reminds me too much of the Duskling from Magic of Incarnum. d8 HP, full bab, good Will and Fort saves, martial weapons and all armor with the abillity to cast in light armor w/ no ASP, eventually growing into Medium, and then medium and heavy shields. Class can cast spells as a swift action a certain times per day, and can channel touch spells through their weapons a number of times per day.
I tend to agree with Nightfall, I like the AE Mage Blade better, but
I have a certain fondness for this class as well. Full Bab and the sheer number of spell slots this class can have is impressive.
Knight: Keeping it short here as most people have seen the preview of the class on the WOTC site. I like the class, it does feel very Sturm Brightblade to me, which is a good thing. People's complaint that the class abillity feels to much like a MMORPG is a bit silly to me. Being able to draw a creatures attention is a very valuable power, and one that frankly has not been modeled in D&D well before. When most DMs say that when a character goes unconscious in the threat range of an oponent and they DO NOT finish them off, we can see an area of the game where people's behavior has adapted to negate a hole in the rules.
Kudos to WOTC.