R. Scott Clark has posted a series (so far two, I'm not sure if more are in the works) drawn from the works of William Perkins (1558–1602) discussing what constitutes true Catholicity. (part 1)(part 2)
In general, both Clark's and Perkins' comments are excellent. Clark notes, "Vatican II changed none of the doctrines against which the Reformation reacted." I would caveat that with "almost none" or "none of the major." Of course, on these points, a "conservative" Roman Catholic might argue that the points of change were never doctrinal issues, despite the fact that things like the use of Latin to the exclusion of the common tongue, forced celibacy of deacons, and rigid rules for orders were defended by Rome's advocates on doctrinal grounds.
And Rome has worsened her doctrines in several ways, in addition to what Clark mentions, Rome has subsequently made the Bodily Assumption and Papal infallibility dogma. Moreover, the exclusivity of Rome has certainly be downplayed to the point where inclusivism is rampant throughout the Roman hierarchy.
Clark states: "Perkins was concerned about a false ecumenism then and we have just as much right to be concerned about it now." Just as much, and perhaps even more. Rome is approaching ecumenism more winsomely today than she did back when she was having the Reformers imprisoned and burnt at the stake.
UPDATE: Part 3 is up (link).