Application startup without any solution/project should be instantaneous (less than 1 second)
Application shutdown should not exceed 100ms for each open project and should show a progress bar.

Building currently completely blocks the UI, and no progress is shown. Just showing a responsive, non-blocking UI windows which shows progress and has a working cancel button would be a great addition.

Larger solutions can take a long time to load. Make it faster, so I can get started on my work right away.

There is a visible lag between the moment you press a key and the moment this translates into a character on the screen. Things like Go To Definition, and scrolling, can hang for several seconds.

It appears to get worse over time as you work in the editor.

It often takes several seconds for a XAML Window to fully display. The editor is constantly pausing as I type, sometimes for as long as a second, before catching up with keystrokes.

It takes too long to begin debugging an application. It also takes too much time stepping through code in debug mode.

When you open 10 files or more, change between thems or close all is slow, more if some of the files are designers (WinForms, xaml)

Intellisense for VB, C#, C++ should be faster.

When projects and solution is regenerated outside of Visual Studio, and Visual Studio picks detects the change and offers user to Reload or Ignore, it offers one or two dialogs per project. There's no way to "Ignore All" or "Reload All". This is low-cost high-impact feature for many developers who generate their solutions and projects using external tools.

Clicking on that option often takes 5-10 seconds and it completely hangs the GUI.

R# is a super popular addin and dramatically slows down VS startup. This situation certainly impacts negatively the VS startup issue many are complaining about.

Through he VSIP program R# guys and VS guys should meet and see how the R# bulk code (>40MB of dlls) load could be smartly deferred when the user is choosing a sln / loading a sln / starting work with a sln.

C# and VB.NET compilers are blazingly fast! However, on RebuildAll scenarios, the user experience could be (easily) enhanced if:

1) The progress bar would show accurately the RebuildAll progression.

2) If before compilation, VS could warn/break if one or several target DLLs WndHandle are currently hold by some processes, and which process hold which handle (the process explorer way)

3) RebuildAll doesn't try to recompile DLLs relying on DLLs that didn't compile successfully.

Separating designer from xaml text editor will allow use them on multiple monitors. Also it takes times to open a xaml file because the designer loads. Even if only xaml text editor is visible. I prefer to edit xaml manualy and don't need the designer. If i need it some day, i will open it explicitly

When you right click an item in Solution Explorer in particular the menu it is very slow in appearing. Make that faster and snappier. Context menu in editor is also slow, and can be improved too.

With a lot of extensions installed, the source code editor can really slow down on some older systems. Scrolling isn't smooth, and typed text can have big delays in showing up.

It still takes a long time to load the Add Reference dialog, and even after it loads, it is very slow to use.