The server had some massive lag at times while zerg was fixing things; not uncommon on any server when there's a huge update.
If you feel it is your computer though, have you tried optifine? If not, install it,
optifine.net/downloads, and play around with the video settings to see if that helps any.
Also, i've read that there have been issues for some that if they use a 1.7 texture pack in 1.8, they've noticed extra lag.
I hope you are able to come back to play soon.