Possibly of relevance to a few people here (especially outside the US). A few months ago the USGS made some substantial changes to their data download that have made their downloads a) faster and b) more reliable. My data downloading had slowed for a while as I could only successfullly download data for a couple of hours a day which was a real pain (60Mb data tiles would crash at 90%+) but it's now working beautifully 24 hours a day. The queues occasionally get a little long but the downloads rarely crash and there's a now a link to retry the download for an hour if it does.
Filled my new hard disk... got an extra 1Tb now

Some more terrains will be coming in the near future.