Would you like to elaborate on that? Obviously going out of TW will also bring some disadvantages, like the use of the S PEN, and some TW based applications which I quite enjoy: the S Note and the S Planner, just to name a few.
Obviously they can be replaced - however not something everyone is willing to do.
The major thing for me with the stock ROM is the lack of space for installing applications. Nothing is more irritating than receiving a brand new update of your favourite application and when trying to install it and get the "not enough memory" error.
I for one did get annoyed enough to try the SlimBean final stable version, and I did not go back. The ROM is fantastic, and extremely light. I had to install some new applications like the Business Calendar Pro and the matching Business tasks which I learned to enjoy (even though the visual aspect of the S Planner was better in my opinion). I also substituted the S Note with Evernote, Sketchbook mobile express and Papyrus and now it looks like a new phone.
However its not like I gained a new feature with 4.3.1 over what the stock ROM had. But after about 2 years of using it, it was taking too much time to open some applications and the general lag was all over the place. Now its not a Galaxy Note 3, but I am quite happy with this change.