Today I will start by Comparing Blackberry OS 4.6 To 5.0 Just To Note The Differences And If You Have Not Updated To 5.0 Yet This Might Be Useful For You!
So Let's Begin -
1st. The Theme on OS 5.0 is much more polished and looks much better than 4.6
2nd. Now Except there being a app for Media there is a folder so for Curve 8520, 8530, Pearl 3G 9100, 9105 (Because of the music keys on top) it is much better as now everything is sorted into a folder for example - Music, Ringtones, Images, Camera Etc.
3rd. The phone runs a little bit smoother and the add-on for Transitions in Themes between menus and home-screens i think looks stunning as it gives your phone sort of a good feel and look to it.
4th. There have been a few Icon changes in OS 5
5th. The profiles selection on the home-screen is much to better for your on custom preferences for sounds better than OS 4.6 in my experience.
5th. In the Images app now you can scroll using your Trackball/Trackpad rather than using "N" And "P" which you still can again personal preference.
6th. In the Messaging App you now have Threaded SMS just like BBM (Blackberry Messenger) which according me looked better, Other than in 4.6 all the messages kept on adding and eventually you had to delete Messages hence in this OS you wont have to!
7th. The Boot-Up screen looks much nicer and does Boot-Up a bit faster rather then just have a Hourglass in 4.6 which sometimes scared me, But in OS 5 it has the Blackberry Logo and underneath that a status bar to tell you the progress of Boot-Up really neat feature!
8th. Now when u lock your phone or let it be idle the screen doesn't just black out, In OS 5 it eventually fades out rather than just blacking out.
9th. You have got couple of new settings in the Options menu.
10th. You also get a cool looking Ice wallpaper in Sample pictures in Images app and it looks pretty good (I have a Curve and only seen it on Curves)
11th. Everything loads much quicker and you see less of that little Hourglass, In 4.6 I used to see alot of the Hourglass.
In My opinion the OS 5 is terrific and Rim has certainly done a excellent job with it!
If you are still with 4.6 dont worry and just upgrade to OS 5 I am sure you will love it!