In the first wave of "Morph" ice Changeling is the most stable of the 3 cards.
For its ress cost it is one strength lower then another 5 priced ice the Fire Wall, and has the same influence cost. For the purpose of taxing this makes changeling vastly inferior, unlike Fire Wall however this guy can change into a Sentry form, making him slightly more useful for actually ending runs when it matters.
-Can become a 4 strength sentry that ends the run for a total cost of 6 and an extra click, a fair price compared to Guard.
-Not counterable with an unmodified Mimic. Some icebreaker suites may have to spend unreasonable to get through.
-Bad tax in barrier form.
-Countered somewhat by AI breakers.
Changeling shines in a strategy that focuses on denying the runner breakers, if you manage to kill a certain type of breaker Changeling has a good chance of being able to morph into that type and lock the runner out. Especially if you target sentries.