Harley n co. Our experience with immunisations has been just fine. At Natalie's 2 month shots, she was unsettled in the afternoon and refused a sleep. We gave her Panadol at lunchtime, lots of cuddles and breastfeeds, then Panadol at bedtime (around 6pm) and she slept the night through. She has never had reactions (as in fever) to the injections, only sore legs with little bruises. She hasn't been really unsettled after either the 4 or 6 month ones. I still hate them, of course LOL. My advice would be if you are upset, take your DH or mum or friend or whatever along with you if you can Hope it all goes well for you today.
ETA: I always wait to give Panadol too - I believe it is pretty fast-acting...