Just to beat this horse some more I climbed Standard yesterday with 2 clients who had 1 previous day experience, the day before, at Square Ledge with me. We started at 9am and climbed via the Arch and the 5.7 finish to the top. We climbed one at a time on single ropes (9.8's) and we topped out at 11:30am.
2.5 hours, and we were not rushing. Another local guide with 2 clients did Sliding Board at virtually the same pace, though I don't know the experience of his clients.
My point is the main thing that slows you down on moderate (read 5.7 and under) slab is;
1) Onsighting, mainly because of routefinding challenges
2) slow seconds... you can see good body position on the arch on the last picture:http://davidlottmann.wordpress.com/2012/05/28/rock-climbing-fast-track-course/
A party ahead of us had started up Slabs Direct thinking it was Standard Route.
They did have the nice watercolor P. Lewis topo map but were new to the area... I'm looking forward to seeing the detail in the new Handren guide.
Certainly a big speed increase was running out long sections of the arch that I would encourage new leaders to place more gear on. That and familiarity with the crux pitch.