after an upgrade from a lower version to a higher version, it's pretty much mandatory to rebuild statistics with fullscan;

the update engine uses different statistics/uses them differently, and performance is known to suffer until the stats get updated.

you'll see a lot of topics here like "new server slower than old server" here; it's a common issue.

updating the stats might take five minutes at the most, but you'll see performance increases immediately. edit] the code below took 3minutes and five seconds to run on my 2008R2 8 gig production database and 27 seconds on a 50 meg database with 1500 tables.

DECLARE @Exec VARCHAR(MAX)

SELECT @Exec = ''

SELECT @Exec = 'UPDATE STATISTICS ' + QUOTENAME(schema_name(schema_id))+ '.' + quotename(name) + ' WITH FULLSCAN ; ' + CHAR(13) + CHAR(10) + @Exec FROM sys.tables ORDER BY name DESC

PRINT LEN(@Exec)

PRINT @Exec

EXEC(@Exec)