I have the Givi E52 and love it, and it's a 4 point mount vs 3 point on the Yamaha, plus it's 42 vs 45 liters. Only downside is the extra key you have to carry.

Oh, and it's $300 CHEAPER than the Yamaha trunk and mine is color matched (2003 silver). I actually think it looks better than the Yamaha trunk. Plus check out the new mount under "Parts and Accessories".

Marc