Part of this problem is due to the Android runtime that's used to execute the applications. Right now, it's based on the ancient Android 2.3 Gingerbread, which we all know is one terrible OS as far as user experience and responsiveness goes. But fear not! BlackBerry has announced that it's going to update the runtime to the much more modern Android 4.1 Jelly Bean. Exactly when this is going to happen is unknown, but when it does, it's expected that the performance of Android apps on a BB10 device will get noticeably better.
BlackBerry is using this kind of emulation technique in order to get an early boost in the amount of available applications for its brand new BlackBerry 10 operating system. The company boasts that it offers over 70,000 apps at launch, which is a really good number, but that number would have been significantly lower, if it weren't for the Android ports. Offering these Android apps shouldn't be considered as some kind of unfair move by BB, because it is the developers themselves who have submitted their apps to BB's applications store, knowing that BlackBerry's new devices will support those apps. Sadly, it seems no one has bothered to optimize the experience for the users of those device. Let's hope that the Android runtime will be updated soon, and that this will bring a substantial performance boost.