Apparently he's been the best GK in Serie A this season. Better than Buffon.
I'd still get someone like Ter Stegen, Courtois or De Gea over him though. Especially if the rumor of him costing 30m is true.
Handanovic is much better than all 3 you've mentioned, they're young keepers whereas Handa would fit right in. The whole he has to pass and be good with his fit is BS. De Gea won't move, Ter Stegen i'm not sure how much he'd cost...+ he's german which brings it's own difficulties (I'd rather have a more experienced keeper in that case). Chelsea will never sell us Courtois, moreso if Mou moves to Chelsea next season.
If Handa costs less than 15 mill then we should go for him. If he costs more then maybe think about raiding United for De Gea. Inter might be forced to sell if they don't get CL football which looks likely.
Martinez is a much better option than the other names being touted as potential CBs: Silva ishas a contract until 2017 and is being paid insane wages at Paris+ he likes it there.
Kompany has been off form for a season now and we've already got an off form CB, plus he would cost a lot of money, remember you're trying to buy from City.
Vertonghen will cost a lot, he's happy at Spurs+ they'll almost certainly sell Bale already so won't have any need to sell Vert.
Hummels - injury prone and german+ Dortmund won't sell anyone else, they openly said this. Gotze and Lewa are already leaving so I don't see them destroying their entire team.
Martinez isn't a WC cb but he's young,spanish, cheap and potentially WC. Besides with all the options we'll have next season if fully fit we'll need a CB like him that won't mind being rotated.