So far, Scala 2.11 the most painless major version increment I've seen. Most of my projects compile with no problem. The following is one of the few actual errors I've run into:
[error] /home/stucchio/src/breeze/src/main/scala/breeze/linalg/DenseMatrix.scala:51: in class DenseMatrix, multiple overloaded alternatives of constructor DenseMatrix define default arguments.
[error] final class DenseMatrix[@specialized(Int, Float, Double) V](val rows: Int,
Apparently 2.11 is being stricter about default arguments in constructors. The fix is fairly straightforward. In 2.10, your code might look like this:
def this(rows: Int, data: Array[V], offset: Int = 0) = ...
In 2.11, you need to do this:
def this(rows: Int, data: Array[V], offset: Int) = ...
def this(rows: Int, data: Array[V]) = this(rows, data, offset)
Just throwing this out there in case someone is googling.