That is not the way to gain new customers. It is just adding doo-dads, usually in a confusing and insufficient manner. Sometimes less is more if the less is workable and the more is not.
Think of the various types of calligraphy. The tools are very simple and limited and yet what beautiful results can be produced! But the tools have to work and not be continually presenting problems or unnecessary choices to the artist. What even more beautiful results could be produced with Mathematica - if the basic interface allows the writer to concentrate on his or her ideas.
Mathematica cannot directly provide all mathematical services because there are just too many possibilities and the people at WRI are not expert enough in all areas and do not have the time or experience. Many useful applications will be specialized in some respects but will have many extra convenience routines for the particular application. WRI has to concentrate on providing core routines both for mathematical calculation and basic presentation constructs. It may be difficult to decide what should be a core routine, but just adding on things willy-nilly is not likely to succeed. Good add-on Applications should be a basic mechanism for extending Mathematica. WRI does an extremely poor job at explaining how to write Applications and the Workbench support is only barely adequate. (I do have a rather extended discussion on writing Applications in the Presentations Application, including where to put them, how to set up folder structures, and how to provide certain and convenient access for users - for those who might be interested.)
The entry point for input to a Mathematica notebook should be absolutely CLEAN with NOTHING there except what has already been entered and the entry point. If the writer needs assistance he should request it. Without requesting help it should be invisible. The basic methods for requesting assistance should be hot keys or the right click context menu, or possibly the Mathematica Menu. Why couldn't Wolfram Alpha be on the context menu instead of an in-your-face doo-dad button on every new Input cell, which also appears and often gets in the way of text in created windows? Some of the choices there are already on the context menu. And there is a WolframAlpha routine. And you can also get it just by typing ==. I wonder what percentage of Input cells become WolframAlpha? It is a nice but occasional feature. It isn't worth sacrificing a clean interface when there are so many easy alternatives.
WRI already makes a fair use of the context menu and they could make even better use. In Windows one can right click within a folder and get a New entry on the context menu. One of the new items that can be created is a Mathematica Notebook. It would be very nice if they could add a Mathematica Package to the list. (Maybe Microsoft creates the list from installed applications and WRI can't control it? Or can't set .m files as a file type?) Once one has set up a proper Application structure it is really easy to write packages. Getting the package in the right place is another little speed bump that deters writers. In Input cells the context menu has an "Insert Special Character..." entry. This would also be useful in Text and text like cells, where it is missing. It would be nice if spell checking was on the context menu for Text cells and the various Section cells - to just check those selections.
As for the Suggestions Bar after output, I think it is rather dubious for most writers to have WRI rewrite their code. But I recall that one poster said he liked it because it reminded or introduced him to routines that he was unaware of. Which suggests that a really useful feature would be somewhat different. Why not have a "See Also" context menu entry for Input cells that brought up a list of relevant routines and links to their Function pages. This kind of targeted and selected shortcut into Help would be quite useful.
One built-in feature of Mathematica that seems inadequate to me is Grid for constructing tables. I wonder how many people use Mathematica to write custom tables, say with blocks with different background colors, and special dividers and fonts and things like that. Tables are an important method of conveying technical information and I wonder if the difficult Grid construction dominated by Option programming mitigates against using Mathematica as a communication medium.
It would also be interesting to know how much use the new "add-on" features such as units and tensor get. It would be nice to hear positive or negative comment.
Although I'm a heavy user of Mathematica, I may not be typical and my suggestions might be off the mark or just plain incorrect. Nevertheless I think public discussion of where Mathematica should go can only be helpful.
As a possible, simple-minded explanation of what WRI is up to: surely they're faced at any given time with a given customer base. To gain new customers, they need to add new areas of applicability, whether through adding them directly to Mathematica or by creating new Mathematica-based products.