My son and I own a welding shop.
We have both the 8 1/2" Milwaukee metal cutting circular saw and their metal cutting chop saw. They are about 6 years old now and they get used often. We haven't had any problems with either saw and would replace with same if a problem did occur. Blades are the only parts that have needed replacement.
Blade life is very dependent on how you use the saw. For the circular saw, ALWAYS use a saw guide, as any binding of the blade will damage blade teeth. The 7 1/2" metal cutting blades from Harbor Freight are slightly smaller in diameter, but much cheaper in price and last about the same as the Milwaukee and Freud metal cutting blades costing 3 X more. We are now using a store brand blade from Northern on the chop saw and it is holding up well. Don't expect these blades to last anywhere near as long as their wood cutting counterpart, but if you don;t follow my suggestions, you can destroy the blade in just one cut..
I mounted the chop saw to a Delta hand truck style miter saw/planer stand that is no longer available, but a slightly better version of the same stand design is now available from DeWalt.
http://www.northerntool.com/shop/too..._content=50287 .
I also installed a 12" lazy Susan bearing between two plates under the saw. The lower plate is attached to the stand and the upper plate is attached to the base of the saw. This bearing lets you turn the saw to match the position of your stock when cutting miters, much like you can with a wood cutting chop saw. None of these saws offer the pivoting function and this works quite well. The saw is left attached to the stand, so it can be rolled around easily, left standing on end in the corner of the shop, and even slid into and out of the truck easily. Gas springs in the stand help you lift the heavy saw into the raised work position. Pictures of our saw and stand are attached. If you do this, get in the habit of cleaning chips off the saw and table before tipping the stand up on end. If you don't, chips will get into the lazy Susan bearing and jam it DAMHIKT.
For both saws, commit yourself to the cut and follow through all the way to the end of the cut. If you stop mid cut, the spot where you stopped will work harden and damage blade teeth when you resume cutting again. We cut almost everything up to 1" thick with these saws. They aren't as fast as cutting wood, but the edges of the cut look almost like they were finished on a milling machine.
We also have a DeWalt 19 volt cordless metal cutting circular saw. It doesn't see much use, but it is great to have when working off a scaffold.
Wear safety glasses, long sleeves, gloves, a full face shield, and button your shirt fully up to your neck, A leather apron is a good idea too. The chips are HOT and fly everywhere, even though both saws have chip collection.
Charley