At least in my MacBook I can notice marked speed increase when loading 100% previews. That’s very nice because Aperture have been quite slow earlier in that respect.
I have been eagerly waiting for RAW support for X-Pro1 in Aperture. It is still not included even if there is already X-E1 utilizing the same X-Trans sensor. Now many people shooting RAW are going over to LR because it can do the conversion (even though it is not perfect yet).
Oh let’s see. I do not have any high hopes for Aperture 4 anymore. I am mainly using LR now but going back to Aperture now and then.