2 months ago we upgraded from BI4.0SP7 to BI4.1SP4. We had no issues, other than scheduling reports to inbox/ email/ftp from BI launchpad in browser IE9/10/11 (Browser freezes). At that time SAP said they were going to fix that in next SP. Now there is SP5:
SAP BusinessObjects Business Intelligence Suite 4.1 SP05 (SP5) Released
Unfortunately we have Data Services, Information Steward on same box (which is not recommended), had to deal with other issues related to them. But overall 4.1 SP4 looks good !!