I've been playing a lot of 8th and did play a lot of 7th. 8th is _very_ different. Much more streamlined and quicker. Originally it was also much easier to keep all the different rules in mind as well, but that's been changing with the usual GW need to add a billion books all with new rules. There are some things I miss from 7th. The templates are gone, and so is the front/side/back of vehicles. Both made things far more tactical. No more can a flamer wipe out two units with good positioning, nor can you ambush a vehicles rear to have an easier chance of damaging it.
That said, I found my games are nearly twice as fast now. Generally I quite like 8th, but for people who played a lot of previous editions I know it was quite a shake up.