Criticisms of Kant's expositions of space (+Time)

Ok now Ive finally pretty much understood what Kant is going on about in his Aesthetic.

I see that (he says) space and time are the forms of appearance and are necessary for experience to take place.

I would like to get a discussion going on what criticisms people have about his 4 arguments of space/time plus the traqnscendental expositions or anything else related to this area of the critique as a whole.

What are the main problems which aris with his arguments? Plus sources from other thinkers to support this if poss, thanks.