The lag on scanning events with DHL is up to around half an hour (that is, a scan made at 1pm might not show until 1:30pm), other than that it's pretty spot on and as mentioned above, they are hands down the most efficient courier service I've ever dealt with (as a recipient).
I can't speak for other drivers, but mine will ring / knock if I'm not at the door when they approach, I think I've only ever had to reschedule a delivery once and it came the next day as requested (unlike so many others, who confirm you've scheduled re-delivery for the next day, then they show up 3 days later). You can also provide Authority to Leave, which means the driver will leave the package without collecting a signature, if you're not home or able to answer the door.
Just in my own experience, they fly the packages directly to my state (most other couriers fly packages to an interstate headquarters and then truck them out to other states), so they're generally faster and 99% of the time, deliver the same day it clears customs (if it's a week day), so keeping an eye on the tracking is a good idea (most of mine hit the ground early morning, clear customs mid-morning, are loaded for delivery early afternoon, and then delivered mid-afternoon).
