I think he's a decent player when it comes to skill, vision and delivery but also comes with some big flaws like tracking back, defending, lack of goals, lack of pace etc. Pound for pound this will be a complete bust footballing wise.
People are going absolutely berserk and comparing him to Iniesta and whatnot - completely over the top. As a partner for KDB in midfield this will not work, and playing him as a LW would be counterproductive given his lack of pace. I had to do a double take, but he's scored 15 goals in the Premier League and 14 goals in the Championship for Villa in about 7 years. His football contribution to City will be marginal at best. Kane on the other hand is a different kettle of fish, that's someone they actually need.
But back to Jack and this 100m quid transfer. He seems to be very well liked by the general English public. I think this a PR move from City to further sportswash their soiled reputation in the game. Paying for goodwill is Abu Dhabi's MO, it is the reason why they bought City in the first place. Spending 100m quid on the darling of English of football (and maybe 150m quid on Kane next) buys them so much widespread acceptance and positive spin in the media that completely washes off all the dodgy sponsorship deals, the FFP cheating and the general stench of the Abu Dhabi regime. Who cares about slave labor when 'our boys Jack and Harry are playing under Pep in the CL tonight'. It will completely shift the narrative and that's what City desperately wants.