Haste is not too dangerous if your concentration and defense is good enough. Which may be questionable or not. I believe the bladesinger is fine with haste. Depends on the situation.
The only real concern is extra attack not mixing well with the new cantrips. But as a weapon user it may come in handy in different situations.
Yea, most things aren't going to drive your concentration save higher than DC10, and with lets say CON resilience, Warcaster, and the innate SS ability, you're realistically going to have +8 with advantage by 8th level to +13 with advantage by 19th level.
Above 17th level, we get to cast Shield and Misty Step forever at 18th level, though I don't really see an advantage to the 20th level wizard ability so I would probably throw a level of fighter in there for dueling and get the +2 damage.
By 20th level (without magical items) we have a character that looks like this...
3 attack @ 1d8+10 damage (while hastened and with advantage from Foresight)
1 attack @ 1d8+ 2 damage if we use our bonus action for an offhand attack
That's an average of about 50 DPR if all the attacks hit, and more like an average of 62 DPR if magical items are thrown into the mix.
AC21 (AC26 as long as I have a reaction available with infinite Shield spells) and the enemy attacks with disadvantage with Foresight. With magical items thrown into the mix we are going to basically be unhittable
The ability to blip around the battlefield as a bonus action with Misty Step without using spell slots
A substantial hit point buff from the ability to convert spell slots
incredible role flexibility from a full 9 levels of spells