You may want to try upgrading to the latest JQuery Mobile. I believe it has some new features that will detect if the device has hardware acceleration and change it's use of transitions/animations appropriately. I have not tried this on Samsung Galaxy.
Also you may want to turn off transitions. You can do this by adding one line of code to the layout.erb file
$.mobile.defaultPageTransition = "none";
Forgot to include the link to the release I was mentioning:
Also if you do a search on jQuery Mobile Slow on Android you will see several threads that have some suggestions. All of this depends on many variables including your DOM structure, etc
Android devices running Gingerbread or earlier do not have hardware acceleration in web views. Using the latest RhoElements and Motorola WebKit will give you some hardware acceleration on those devices.