You should be aware that SQL Collations are going to be depreciated.

Another thing is use of TERTIARY_WEIGHTS function that could kill performance of any server if you use SQL collations.

In other terms - use of SQL collation and ANSI defined columns (char,varchar) in some cases(queries) yields use of TERTIARY_WEIGHTS function and table scans no matter if you have index on column or not. If you have big tables it could be a very big problem.

So, if you can, go with clean install with windows collation. Also, change database collation and column level collations to the same - windows collation.

A good starting point to go deeply is http://blogs.msdn.com/michkap/default.aspx

rgds

Sinisa