Mike's quite right that having an FIS should not be taken to absolve the pilot from prior checking of NOTAMs, but it does have the virtue of being more up to date. I have to check the NOTAMs from home, there's no facility to do so from the airfield, and I have to leave home at 0700 to be airborne at 0900, then might not get to see a NOTAM all day if I'm flying between little grass airfields.
If a Soham / Hatfield situation breaks out during the day, only an FIS is likely to keep me out of any unexpected TRAs that spring up.