I've just installed CM10.1 on my Galaxy SII, it feels like a new phone! Fell in love with my phone all over again 
I'm currently just running the ROM and some of my favourite apps. For the last year and a half, I've been on stock ROM's (2.3, 4.0 and 4.1.2) with Apex Launcher (a brilliant vanilla Jelly Bean launcher). Thought I'd give some of the pro and cons of a custom ROM vs a stock ROM with Apex Launcher.
Pro's of using the stock ROM with Apex launcher compared to CM10.1:
1) You don't have to root or flash a new ROM (for people who are scared of this)
2) New drawer tabs can be created in the app drawer (can't be done in CM10.1, this is a major drawback for me!)
3) Folders can be created in the app drawer (can't be done in CM10.1)
4) Great theme support, change app icons, folder icons (can't be done in CM10.1, except if you root as I understand)
5) Awesome gestures, swipe up, two finger swipe up, two finger swipe down, that can be assigned to anything (can't be done in CM10.1)
6) Can change the app icons size in the app drawer and home screens (can't be done in CM10.1)
Pro's of using CM10.1 compared to the stock ROM with Apex launcher:
1) You don't have to use a launcher, as the default launcher is already the vanilla Jelly Bean experience.
2) The vanilla apps like Calender, Messaging, Phone, is installed by default (No need to download them separately and have two of the same functioning apps)
3) Much better notification centre compared to TouchWiz. Split into notifications and quick settings (which can be customised)
4) Much smoother compared to stock with Apex.
5) No bloated apps that come with the installation.
6) Notification bar is blue (functionally does nothing but looks awesome!
)
7) The battery icon can be changed to show percentage (great feature)
8) Awesome lock screen with lock screen short cuts and extra "lock screens", where if you swipe right, you get the camera and if you swipe left, you can add your own lock screens with widgets on.
9) Once CM10.1 is installed, the nightly updates can be applied OTA, so you don't have to go through the whole flashing process again, which is great
10) Notifications bubbles (the red numbers above the apps) are built in and works great, with Apex, Apex Notifier has to be installed for and sometimes doesn't work (although, with Apex Notifier, the bubble colour, position and shape can be changed, which is cool
)
There are a lot of features both CM10.1 and Apex can do, compared to TouchWiz, which I didn't mention, for the people that just want to try Apex:
1) Change number of rows and columns in home screens.
2) Change app names in home screens.
3) Hide apps from in the apps drawer.
4) The dock at the bottom can have multiple "screens", so if you swipe left or right you'll have extra icons in the dock.
5) The dock and notification bar can be hidden.
6) The home screen and drawer swipe animations can be change, for example, flip, cube out, cube in, rotate etc.
There are probably a lot of features that I missed, but these are the important ones for me. If I made any mistakes, feel free to correct me
I'm currently just running the ROM and some of my favourite apps. For the last year and a half, I've been on stock ROM's (2.3, 4.0 and 4.1.2) with Apex Launcher (a brilliant vanilla Jelly Bean launcher). Thought I'd give some of the pro and cons of a custom ROM vs a stock ROM with Apex Launcher.Pro's of using the stock ROM with Apex launcher compared to CM10.1:
1) You don't have to root or flash a new ROM (for people who are scared of this)
2) New drawer tabs can be created in the app drawer (can't be done in CM10.1, this is a major drawback for me!)
3) Folders can be created in the app drawer (can't be done in CM10.1)
4) Great theme support, change app icons, folder icons (can't be done in CM10.1, except if you root as I understand)
5) Awesome gestures, swipe up, two finger swipe up, two finger swipe down, that can be assigned to anything (can't be done in CM10.1)
6) Can change the app icons size in the app drawer and home screens (can't be done in CM10.1)
Pro's of using CM10.1 compared to the stock ROM with Apex launcher:
1) You don't have to use a launcher, as the default launcher is already the vanilla Jelly Bean experience.
2) The vanilla apps like Calender, Messaging, Phone, is installed by default (No need to download them separately and have two of the same functioning apps)
3) Much better notification centre compared to TouchWiz. Split into notifications and quick settings (which can be customised)
4) Much smoother compared to stock with Apex.
5) No bloated apps that come with the installation.
6) Notification bar is blue (functionally does nothing but looks awesome!
)7) The battery icon can be changed to show percentage (great feature)
8) Awesome lock screen with lock screen short cuts and extra "lock screens", where if you swipe right, you get the camera and if you swipe left, you can add your own lock screens with widgets on.
9) Once CM10.1 is installed, the nightly updates can be applied OTA, so you don't have to go through the whole flashing process again, which is great
10) Notifications bubbles (the red numbers above the apps) are built in and works great, with Apex, Apex Notifier has to be installed for and sometimes doesn't work (although, with Apex Notifier, the bubble colour, position and shape can be changed, which is cool
)There are a lot of features both CM10.1 and Apex can do, compared to TouchWiz, which I didn't mention, for the people that just want to try Apex:
1) Change number of rows and columns in home screens.
2) Change app names in home screens.
3) Hide apps from in the apps drawer.
4) The dock at the bottom can have multiple "screens", so if you swipe left or right you'll have extra icons in the dock.
5) The dock and notification bar can be hidden.
6) The home screen and drawer swipe animations can be change, for example, flip, cube out, cube in, rotate etc.
There are probably a lot of features that I missed, but these are the important ones for me. If I made any mistakes, feel free to correct me
But the combination of CM10.1 and Apex rocks 
