There are a lot of articles revolving around Laravel 4 specifically that try and explain how to abstract logic away from your controller, but most of them either kinda miss the point or overcomplicate things (by using facades, repositories, interfaces...).
There's been some discussion around Laravel and SemVer (semantic versioning) recently, which I appreciate. SemVer is in my eyes a very important guideline for frameworks and widely adopted libraries.
Testing mails in Laravel 4 is a bit of a weak spot. You can say
Mail::shouldReceive('send')->once()... but specifying everything the method should receive in terms of arguments as well as asserting that the closure sets the recipient and subject correctly is tedious at best. This SO answer shows an example of how to unit test a mail being sent.
Mocking classes and defining what methods they should receive is easy.
I love the Laravel 4 FormBuilder (accessible through the
Form:: facade) - automatic re-populating of input from the session and from a model is awesome. In the upcoming versions you will even be able to use accessors to populate form fields from the model even if they're not actually fields in the database.
Repositories have their place in applications that deal with fetching stuff - either if it's from a database or an external source. In the Laravel world the repository pattern has been praised a bit too much for its advantages in terms of testability and architecture. I've written about how you can achieve the same level of testability without repositories, but sometimes repositories really are recommended.
There's a lot of people advocating the repository pattern for testability in your Laravel 4 projects. Fact is, it doesn't make your code that much more testable, and you can easily achieve the same level of testability by using your models as you would a repository.
Documentation on optimization and performance is somewhat lacking for Laravel 4 at the moment. In this post I'll give some quick pointers as to how Laravel 4 works and how you can improve its performance.