I'll put in my endorsement for Kriega's products. I picked up a US-30 last week based on some threads here.
I have a 2007 ex250 so I can use the nylon loops that the packs come with or the luggage anchors below the seat, both work well.
The bags seem to be pricey, but what you get is a luggage system. For example you can buy a US-30 and anchor that to the seat, then attach 2 US-10's or 2 US-20 bags to the US-30 bag to increase your capacity.
Also the Kriega bags are dry bags (waterproof), and they are secured in a way in which they aren't likely to scratch your paint
