Revit 2015
The most effective 'new' feature in the Revit 2015 product would have to be the improved Callout > Reference View: Options Bar. In Revit 2015 it shows the Project Views: Dropdown list so you can assign an alternative 'updated' Drafting View to an existing Callout symbol.
You still cannot re-Insert with overrite an improved Dafting View (of the same name) from your Library. You have to accept the incremented suffix number that Revit adds to the Drafting View name and after re-assigning the Callout to the new detail and replacing/placing it on the Sheet, delete the old and rename the new back to it's original name.
At least you don't have to delete the original Callout, recreate it and select a View again!
Revit 2014
The best 'new' feature in the Revit 2014 product would have to be the improved Materials interface. The various Properties dialogs are back as a multi-Tab single dialog.
[V] See How To's By Task - Rendering
User defined Material definition ADSKLIB files seem to save properly now also.
CAD Content is soon to upload an updated RVT Pacifica Library with a new NZ Materials section.
Unfortunately it seems the Structural Beam family template has not yet been updated. We strongly recommend you do a Save... out of the Families > Structural Framing > Concrete-Rectangular Beam.rft from the Structural Analysis-DefaultNZLENU.rte template to use for any custom beam definitions.
When to Stop Modeling
Before starting out on making a Revit Model, it pays to read up on what are considered best practice procedures for the scale of the project envisaged. They are usually guidelines but can often read as directives. We offer some guidelines to consider.
What is the purpose of the Model; for Design & Visualization, Construction Documentation, or perhaps downstream Asset Management; some of the above or all of these makes a big difference on how to model and when to detail.
Parted & Divided Wall
The best new feature in the Revit 2012 products would have to be the Parts and Divide tools for Architectural and Structural users. (They aren't applicable to MEP design tasks.)
Finally after all these years of Revit development and wish list requests, you can now have a lot more editing control over Revit System Families. Multi-Layer 'slab' elements can now be broken into Parts (Layers work like separate sub-components) and if required these Parts can then be Divided (cut into pieces and shape modified).
Parts greatly extend the Visibility/Graphics control of System elements. You can now turn off architectural cladding to document just structural content! Parts can have unique Material and Phase parameter values which then provide extensive abilities to Schedule System Family sub-elements.
If you haven't explored these new features yet, then we strongly recommend you do so and think about how they can be used in your design and documentation procedures.
Portal Frame Assembly
The Assemblies feature is new in both Revit Architecture and Structure 2012. MEP has always had Systems which are in effect an Assembly. (Systems have also been improved in MEP 2012.)
An Assembly is sort of a Group but more so. When you assign a number of elements to be a named Assembly then Revit can do some smart display footwork on the assembly and create additional Views like Sections through the assembly and extract Schedules specific to that assembly.
I can see Assemblies being very useful for Structural engineers. The feature was designed with pre-cast work in mind but is also great for building and documenting things like portal frames. Revit will check for duplicate assemblies and coordinate common names where required.
As for Architectural usage, the assembly can be used for 'grouping', documenting and scheduling elements into specific fabrication items such as Casework (kitchen and sanitary joinery) and commercial fitout Workstations.
Stair Enhancements
Stairs in 2013 have been given significant enhancements. You can now build by components, return and overlap, extended handrails and better annotation.
Components such as flights, landings and supports can all be modified by direct grip manipulation.
Railing transitions and extensions to top rails and handrails have been improved - and you can see a preview of the railing as you sketch it!
Merged Parts
The concept of dividing System Walls and Floors into layer parts was introduced in 2012.
In 2013 this Divide tools can now be used on other Loadable elements such as Structural Columns and Beams.
This means that cast concrete members can now be broken up into segments, phased and scheduled as separate parts of the overal structural ′joined′ frame.
A complimentary new feature in 2013 is to be able to ′merge′ (add and remove) parts into new continuous parts. So two cast concrete walls around a corner can become one L shaped unit.