I have been noting rebuild times, but have been forgetting to include them in reviews.
I've noticed a trend where rebuild times are actually getting shorter. I believe this is because vendors are changing the rebuild defaults to skip the bad block check. Here are a few examples:
Thecus N4200PRO: "Quick RAID" rebuild time for 4 X 160 GB RAID 5 and 10 arrays, under 2 minutes!
QNAP TS-1079 Pro: 4 x 1 TB RAID 5. 2 hr, 30 mins
Before these lower numbers, RAID 5/10 rebuild of a 4 x 1 TB RAID with no other activity would take 8-10 hours.