The SQL Logger is only called after a query has been executed (this was changed to allow profiling of the queries). This makes it difficult to determine which query has failed.

The commit that changed the functionality is at: http://github.com/doctrine/dbal/commit/fe0f0e4b8c6c5308cab3d683c552f61317de7067

It seems that the logger interface needs to be changed to two functions, a pre-query function and a post-query function. Profiling should be handled by the logger if it chooses and not by the connection class.

The ORM has a neat collection of Events, but the DBAL doesn't have any.
There is an DBAL/Events.php class which has defined constants for preExec, postExec, preExecute and postExecute (similar to ORM/Events.php), but these seem to be completely unused.
The only event/loging seems to be the ->logSql() event.

A preExecute & postExecute events would be great for timing/profiling queries.

When connection to mssql server with pdo_sqlsrv driver you get:

 
[PDOException]
SQLSTATE[IMSSP]: The DSN string ended unexpectedly.

Sample $connectionOptions:

$connectionOptions = array(
    'dbname' => 'AdventureWorks',
    'user' => 'sa',
    'password' => 'sa_password',
    'host' => 'local',
    'driver' => 'pdo_sqlsrv'
);

Error is in Doctrine\DBAL\Driver\PDOSqlsrv\Driver in function _constructPdoDsn(array $params).
On line 53 dsn starts with

$dsn = 'sqlsrv:(';

instead of

$dsn = 'sqlsrv:server=(';

as written in offical Microsoft help which come with SQL Server Driver For PHP v2.