I have had the chance to take an in-depth look at the bladesinger, as well as get some player feedback from my group's optimizer (who also got to see it in play on a Virtual Table game), and our consensus is that the class is fucking awesome. The fighter/wizard--aka character that could stab things, cast spells, and be effective--was a pretty difficult concept to realize with either multiclassing (even with 4th Edition) or hybrid builds. I suppose with enough work you could get something functional, but the bladesinger makes it a very easy and straightforward process, delivering an arcane controller that is both effective and unique.
Here is a rundown of each class feature the class gets, along with the sorcerous sword paragon path.
Level 1: Bladesinger Features
Instinctive Attack and Blade Magic all combine to avoid multiple ability and implement dependency allowing you to rely largely on Intelligence and a one-handed heavy blade for attacks and spellcasting. Guarded Flourish lets you get away with casting spells in melee without getting the shit smacked out of you, in addition to giving you a shield bonus with a free hand and light armor (giving you a starting AC on par with greatweapon fighters).
Level 1: Bladesong
This encounter power gives you two turns of insanely souped-up awesomeness; you get a bonus to defenses, attacks, and damage...for starters. At higher levels you can make basic melee attacks as an opportunity action when hit, shift your speed as a move action, and use bladespells even if you miss while its up. The only (understandable) drawback is that you never gain the ability to use it more than once per encounter.
Level 1: Bladespells
There are six in total, but you only get three. The way these work is that if you hit an enemy with a basic melee attack you can followup with one of these. These is no action necessary (meaning you can use it while dazed), but can only use one once per round--so no burning action points to toss a bunch of these out.
- Dancing Fire: Fire damage and causes the creature to grant combat advantage for a turn.
- Dazzling Sunray: Radiant damage and an attack penalty for a turn.
- Frost Bite: Cold damage and slow for a turn.
- Lightning Damage: Lightning damage, and if the creature moves it takes the damage again.
- Shadow Sever: Necrotic damage and the creature is knocked prone.
- Unseen Hand: Force damage and slide 3.
Level 1: Bladesinger Cantrips
This is basically the same selection that the wizard gets; you pick three out of five from ghost sound, light, mage hand, prestidigitation, and suggestion.
Level 3: Arcane Strike
When you use a daily bladesinger attack you get to make a single basic melee attack as a minor action. Nice way to combo up a bunch of damage and conditions without having to resort to action points.
Level 7: Steely Retort
When an adjacent enemy hits you while bladesong is going, you can make a basic melee attack as an opportunity action (meaning you could benefit from this multiple times).
Level 13: Unerring Bladespell
If you miss with a basic melee attack while bladesong is up, you can use a bladespell anyway. Yeah it is a limited window, but every bit helps.
Level 23: Bladespell Burst
Once per day when you use a bladespell against an adjacent enemy, you can use it against each adjacent enemy. I am really glad this is a daily, because it makes it much easier to apply it where needed.
Bladesinger Daily Powers
I am not going to go into thorough detail on each spells at each level, but suffice to say you have a spellbook like a wizard, but you treat a wizard's encounter attacks as daily spells (utilities work as normal). This means that at 1st-level you pick two encounter attacks, prepare one after each extended rest, and use it once per day. The only exception is a level 20 paragon path feature that lets you add an actual daily to your repertoire. In addition to being able to essentially double-tap monsters each round, these provide an additional layer of control.
Sorcerous Sword Paragon Path
Level 11: Choir of Swords
While bladesong is active, you can burn an action point to attack each adjacent enemy with basic melee attacks. This is not as bad as it seems, because you can always trigger bladesong while surrounded in order to benefit from it (along with Bladespell Burst if you want).
Level 11: Boon Spell
You get a new attack spell of 7th-level or lower, and can prepare another spell of any level you can normally prepare (but not the same one twice, which sucks). Hey, free spell.
Level 12: Bladesong Ballet
While bladesong is active, you can shift your speed as a move action. Being linked to bladesong means that at best you will get two rounds of insane mobility.
Level 20: Signature Spell
You can finally prepare a real wizard daily spell, of 19th-level no less. Very nice.