I find it saves a lot of time in the beginning. You just roll for table side, set a few units down, roll for first turn .. and you're playing.
The extra time that Steapa is explaining is simply time thinking, and this time will be reduced as you get familiar with your spell lores and used to the new phase dynamics. In the same way, a new player with 3 wizards of different lores will take a lot of time to figure out what spells to take before the game, and what spell will work best during the game. At least the time taken is now in context during the action - you can plan your next move as your opponent figures out what they want to do.
In addition, you can often throw out a lot of spells. I use cards and the first thing I do is set aside spells I cant use (missiles in combat, out of range, etc). Then I pick out the ones that will be most useful and just go at it. I've been taking Vamps, Shadow and Death and it takes me 5 minutes to do my a magic phase.
I agree that knowing all the lores at once is annoying. I'm suprised that they didn't add a clause where wizards who know multiple lores have to pick only one, or just keep their default spells. The no limit freaks me out as well - I think they should have said a max of 24. The "pick the two highest" for phoenixes and the chaos table is also pretty annoying (as if the new combied chaos and combined elves needed more of a boost).
Aside from these minor things, I think the new magic phase is great. I love jumping into the action quicker.
Also, the minimum number of dice you must use is always one. So you have to waste a dice for any spell attempt.
Assuming you can forgo the + to dispel a spell using 10 dice with your "army" is a stretch. Just as we assume that "broken concentration" no longer applies to the dispeller, I think we can assume that your army counts as a "wizard" for dispeling purposes.