From several reviews, the Milwaukee M18 chainsaw weight 10.6 or 10.7 pounds with bar & chains, but without the battery and with the bar oil tank empty. With the 12 AH M18 battery, it comes to 14 lbs. Filling the oil tank adds about another 0.4 lbs.
I've always felt the Husqvarna 455 was a bit of a pig for weight compared to it's power. The Husqvarna 450 weighs significantly less, and only loses a little on the power as compared to the 455. The Stihl 250 is similar in power to the Husky 450, but weighs about a pound less. The pro-level saws in that power range for both brands are significantly lighter.
When comparing published weights, remember that most gas chainsaws specified weight is for the powerhead only: no bar and chain, and tanks empty. The weights for the Milwaukee chainsaw above included the bar & chain.
I really like the Milwaukee saw. For me it would be a no-brainer, if I ever decide to own one (rather than just trying out my friend's), since I already have a fair amount invested in the Milwaukee M18 products.
Home Depot is currently showing a sale where you can get the saw with two of their 12 AH batteries for $399. However, this sale special comes without their RapidCharger (actually, without any charger). That's OK if you already have one. If you don't, you can charge it with their regular charger, but it takes longer (the RapidCharger is really nice for the larger battery sizes).