I’ve bought a couple of refurbs off Amazon before. It’s pretty much what you expect. Cheap, but they are not going to last long. I never used them in anything less than a RAID 6 setup, and they were the first drives to fail and be replaced. They can get you over the hump of having to order a whole set of new drives at once, but you shouldn’t use more than a few and start replacing them as soon as you can because they may cascade under the load of rebuilding your array.
The one unexpected thing is the drive runtimes were wiped. I could verify by polling the last SMART runs which contained the runtime, and they were in the 4-5 year range.
As long as you buy drives shipped by Amazon, you get their full 30-day return policy. Just run a long SMART test when the disks arrive.
I waited until v10.1.1 to upgrade, and it has been fine. There was too much chatter about battery life when v10 came out so I turned off automatic updates and gave it a few weeks. You can’t always take the complaints literally, but the volume is higher for iffy releases.
Remember, once you upgrade, you can’t go back so it is OK to wait a few weeks. My iPhone 3G was ruined by iOS4 and I wouldn’t consider another iPhone until the 13. I have a manager at work whose default position is “No x.0 versions in our production systems” unless convinced otherwise. (And yeah, we’ve been burned by CA multiple times so it is a valid position.)