Obviously it would be a nightmare to do something like a busy bus station shooting 3 rows of 6 shots. I know a fisheye setup could do it in 2 shots, but that's still too much time between those 2 shots. I saw a Cubic QTVR of an outdoor concert that was pretty cool. Short of a lens I've never seen, or using 2 cameras at once (wouldn't match in stitching???), I can't for the life of me figure out how it was done - and done well, too.
 
Any advice greatly appreciated...

A fisheye is the only way.  I have a sigma 8mm with an xti.  I need to take 5 photos.   I go very quickly and do several revolutions.  You then need to pick choose and mask.  The last one I did took several hours to complete

You are using 8mm sigma with a DX camera I guess. As I understand only one row of 5 images is enough. Is that right? (I am about to buy one) Sigma also has a 4.5mm lens, which would be suitable for making 2 shot panoramas with a DX-sensor camera. Does anybody know whether Sigma 8mm is suitable for two shot panorama using FX camera (Nikon D3 for example) and does it do a good job?

With a DX camera you can get a full 360 with just 4 shots using the Sigma 8mm.
 
No, you can't use the Sigma 8mm for 2 shots with the D3. (Well actually you can if you're very careful but you are then using the very edge of the lens for pixel data so there's some significant loss of image quality). You can certainly take 3 shots though.
 
With the Sigma 4.5mm and a DX camera you really need 3 shots for the same reason as above.