Oh yes! Mine went above and beyond the call of duty (vendor claimed not to know she had to be out by 12.00) so movers were kept hanging around with a full truck for 4 hours. There were 3 of them and I gave them £10 each. Doesn't seem a lot really, but they were only on £80 per day each.
We gave ours £20 each and a case of beer between them. They were delighted - they spend a lot of nights sleeping over in the truck and although they can't drink a lot they appreciated a couple of bottles each night.
I gave ours £20 each. They were really good, worked damn hard and one of them accidentally broke a shelf (my DH saw it and said it was a complete accident, the guy took a step backwards and stepped on it) but told his boss and got our waiting time fee taken off (£60+ it was). I think I felt worse for him than about our shelf! I also asked they re-built my DS1's cot into a cotbed and one of them spent half an hour doing it without the instructions. Bless him! They were Eastern European and I don't think they earn very much. One of them was telling us how the day before, he was on a job till 3am, had 3 hour sleep and came to our job! And they were delighted with the £20 each. If you can afford it and they did a good job, go for it.