One of the nice surprises in the April CTP is that SQL Server 2005 XML schema validation errors come with a location now. That's handy. Here's an example:

Msg 6926, Level 16, State 1, Line 1
XML Validation: Invalid simple type value: '1134'.
Location: /*:Invoice[1]/*:LineItems[1]/*:LineItem[1]/*:Sku[1]

Even better would be a line and column number that points out where the processor thinks this error in a value() method happened.

Msg 2389, Level 16, State 1, Line 4
XQuery [xmlinvoice.invoice.value()]: 'value()' requires a singleton (or empty sequence), found operand of type 'xdt:untypedAtomic *'

I know what was wrong with my query (i.e. what the message means) its become one of my favorite error message because it reminds me that this implementation does static type checking, but WHERE is there an xdt:untypedAtomic *? I guess there's no way to tell me where in a single XPath expression I went wrong, but if there are multiple lines or FLWOR expressions, give me a hint. 

The revised (I think) error at least tells me which "value()" function has a bad query. So if there are multiple value()s in the SQL query and one is wrong, I know which one.

Of course, if I got all my XQuery statements right, I wouldn't have this problem…