I've been stranded by an E190 more than any other aircraft. I love the old seats but hate the reliability and dated everything else.
1. Increase from 100 to 140 seats. It'll take longer to load/unload, get checked luggage...etc.
Doesn't really affect me in any way. I don't check bags. The loading process being 2 minutes longer is negligible for me.
2. B6 version will have the awful & tiny SpaceFlex bathrooms(!) in rear. When announced B6 chose A220, I warned this could happen but everyone said Airbus wasn't configuring SpaceFlex on A220. So much for that!
Untrue as corrected in above posts.
3. Seat pitch will almost certainly be reduced, compared to E190 since that's happened on every new B6 config since all-core A321.
Possibly in EMS but unlikely
4. No middle seats on E190. There's a middle seat on A220 (and saying it's 1" wider doesn't offset that it's a middle seat)
I never choose the middle but the huge upgrade in IFE between the old E190 tiny screen and the newest offerings means I won't care if I'm in there.
Other pluses: Range and a quieter cabin. The changeover can't come fast enough.
I'm still gunning for an all Mint A220-300 for TATL to compete with the Baby Bus. That would be a dream.