Practice varies by count centre, but usually the first count takes so long because ballots are not just counted, but counted and then sorted by second preference before the first count is declared.
I'd also say it's quite possibly the case that we have fewer people actually counting in the average count centre than in the UK.
Logistically speaking I know that Scotland would not have implemented STV for council elections without the stipulation that they are counted electronically. They would have been there all bloody week. Ireland's turnover is not so bad for a hand count.
