Yeah, I agree, it's a pain if the manufacturer removes a feature that you found useful, or messes an app up in another way. It's more annoying is they do something like that with something like the in call UI, which you can't just replace, but it's still an annoyance when they do it to their calendar app, messages, email, gallery or whatever. But it happens. And that's why I always take the attitude that the manufacturer's app is just an app, nothing special, and I treat it like any other app: I use it if it suits me, and replace it with something else if it does not.
(For the record I've never found the perfect Calendar app: there are a number I find usable, but all of them have something I want that they don't do, or which some other apps do better. Hence I actually have several calendar apps installed, and still occasionally look to see whether there are any new or improved ones out there).
