Page splits are not too good for performance and should be closely watched.
One way of determining whether you are having page splits and how many is to use the function ::fn_dblog (@StartingLSN, @EndingLSN). Passing NULL to the two parameters makes sure that the whole log is being read.
SELECT [Object Name], [Index Name], COUNT(*)
FROM ::fn_dblog(NULL, NULL)
WHERE Operation = 'LOP_DELETE_SPLIT'
GROUP BY [Object Name], [Index Name]
ORDER BY COUNT(*) DESC
You can reduce page splits by specifying a good fill factor. There is no real rule of thumb about fill factors. It all depends on the rowsize and number of rows inserted (between index rebuilds). So specifying a good fill factor and a DBCC DBREINDEX from time to time will minimize the number of page splits.