I am working with a table that has columns that start with the word "from" (fromNumber, fromCity, etc). When SQLServerPlatform->doModifyLimitQuery is called, "from" in the names are incorrectly replaced. I suggest adding a whitespace requirement after FROM in the preg_replace on this line:
https://github.com/doctrine/dbal/blob/master/lib/Doctrine/DBAL/Platforms/SQLServerPlatform.php#L848

So this:

$query = preg_replace('/\sFROM/i', ", ROW_NUMBER() OVER ($over) AS doctrine_rownum FROM", $query);

Becomes this:

$query = preg_replace('/\sFROM\s/i', ", ROW_NUMBER() OVER ($over) AS doctrine_rownum FROM ", $query);

When calculating table diffs, SQLServerSchemaManager returns column definitions for identity columns with _autoincrement set to FALSE.

This causes the schema update SQL generation to pump out a
ALTER TABLE x ALTER COLUMN id INT IDENTITY NOT NULL
for every single identity column in the schema.

The culprit is in DBAL\Schema\SQLServerSchemaManager, starting at line 43:

        $dbType = strtolower($tableColumn['TYPE_NAME']);
        $dbType = strtok($dbType, '(), ');

        $autoincrement = false;
        if (stripos($dbType, 'identity')) {
            $dbType = trim(str_ireplace('identity', '', $dbType));
            $autoincrement = true;
        }

When the column in question is an identity int column, the TYPE_NAME is "int identity". The second line of the snippet drops the "identity" signifier, causing the following lines that determine autoincrement to do nothing.

I simply moved the second line to below the autoincrement block ie:

        $dbType = strtolower($tableColumn['TYPE_NAME']);

        $autoincrement = false;
        if (stripos($dbType, 'identity')) {
            $dbType = trim(str_ireplace('identity', '', $dbType));
            $autoincrement = true;
        }

        $dbType = strtok($dbType, '(), ');

This change solves this issue for me, and as far as I can tell, has no other consequences.

In SQLServerPlatform the default length for a VARCHAR declaration is set to "255". But according to the SQLServer documentation from Microsoft the default length is "1", if omitted in the declaration.
See remarks: http://msdn.microsoft.com/en-us/library/ms186939.aspx
Also the default length is hardcoded in the "getVarcharTypeDeclarationSQLSnippet" method which in my opinion should be evaluated through "getVarcharDefaultLength".

I don't exactly know if the current implementation is intended, otherwise it should be fixed. I would then create an PR if desired.