I don't think I'll be going to an Apple Store for an iPad 2, but I have experienced Apple launches in the North East before...
I expected Eldon Square to be pretty quiet last year for the iPhone 4 launch and I couldn't have been more wrong. The queue's lasted for a good couple of hours, winding around those tensabarrier things they put out.
Just be careful, because I seem to remember the store opening at 8am and even then people had bothered to queue for hours. If it's a 12pm or 5pm launch for iPad 2 I'd imagine longer lines.
All depends on supply and demand of course, but its not nice missing out on a product at launch that you've been waiting for!