Got this as gift for Christmas and just had a reason to use it for the first time. Clicks so loud it sounds as if it it coming apart in the front top of the machine. I'm passed my return period which really stinks because it would have gone back in a second if we had used it right off. It only does it under a load. We made frosting which is low load so I'm terrified what it would do if we tried to make bread dough...

Update 4/6/18... It's getting louder. Did some cookie dough and I thought it was going to come apart....

I have used this twice and it replaces a professional 600 model. The pro 600 lasted 4 years!!!!!! that's it. After reading reviews about the people who purchased this commercial model who previously had the 600 pro model had me intrigued to say the least. I make on avg. (6) 20 oz. pizza dough's per week 3 dough's at a time. I will say I did see this skip a little toward the end of the process and that has me concerned. I will say in comparison to the 600 model this is so much more Quiet. The 600 was so noisy!!! I do hope 4 years down the road that I don't regret this purchase.
Well here it is 3 months later and this mixer is sputtering when making 60 oz of pizza dough. I downgraded this Commercial mixer from a 5 star to a 3 star rating.

The mixer is great and performs as expected, but nowhere does it say that the mixer bowl, when new, needs special cleaning that is beyond just hot soapy water before using. After washing it with just dish soap and hot water, I put my ingredients in and got greasy black streaks in my dough which ruined the dough. The bowl requires using a product like bar keepers friend to remove the black residue from the machining that doesn't come off with regular cleaning. I had to go online to find this solution out. Why wasn't this info with the product when I got it?
Once done, it can be cleaned as usual. Fortunately, I had some on hand. There was nothing in the box it came in about this. That was a lot of expensive ingredients to have ruined. (A pound of butter and 2 dozen egg yokes+ all the other stuff)
So, don't hesitate to try this mixer out. I love it now that the bowl doesn't leave unwanted junk on my dough.
I was considering the one with the guard but chose not to get that one. I'm glad I skipped it. Don't need it and it would be in my way.

I am extremely pleased with this mixer! This our 4th KitchenAid mixer in 25 years. All of the others are still running like new - we just needed more. We wanted a heavier model for making various types of dough. Dough is the toughest thing for a mixer to mix. The commercial models have a completely redesigned transmission. I don't know exactly how the transmission has changed internally as they are now sealed and part of the motor assembly but it is now a right angle configuration. Previous models employed several gears which were prone to more rapid wear especially when making larger amounts of dough. It appears the motor is now in direct alignment/coupled with the accessory connection. The entire transmission mechanism is much simpler with fewer moving parts and the result is a significantly quieter mixer. Another benefit of this new transmission design is no leakage of grease as the mixer ages. Previous models after many years would begin to leak grease because the grease would break down and separate. This required periodic overhaul of the gear case where the old grease needed to be completely wiped out and replaced with fresh food grade grease.

The mixer when running at high speed is very smooth. It depends on which attachment is being used and how well balanced it is. We purchased additional 8 quart and 5 quart "J" handle bowls designed for this mixer. The 5 quart is great for making small batches. The only thing is the bowl guard doesn't cover the gap between the top of the 5 quart bowl and the bowl guard because the dimension between the attachment tabs and the top of the bowl is much shorter. We also purchased 1 additional paddle, dough hook and wire whip available here on Amazon so we could prep or clean while another batch is in the mixer.

One other major improvement is the wire whisk/whip. The design uses 11 wires configured more densely in a rectangular profile. We noticed that egg whites whipped significant faster vs our Pro 6. I think it is because the wires are positioned non-symmetrically so they are always whipping through in a different area of the ingredient being whipped.

Everything that could possibly come into contact with food is made of stainless steel including the planetary and bowl guard. The attachments are significantly heavier especially the dough hook. The dough hook is not balanced and the manual warns to not run the mixer beyond speed 2. I ran a test and the mixer will wobble across the counter if it is run at high speed with the dough hook attached. The bowl guard is a great safety feature and extremely easy and non-intrusive to use. We especially like it when small kids are near the mixer when it is running. It will prevent their fingers getting inside where this stronger horsepower mixer would likely cause significant injury.

Have had it for 6 months, it stoped working while i was making pizza dough, at first it seemed really tough,silent, but sometimes make a clicking sound. waiting for warranty since it says it has 2 year warranty. Will keep you updated., next day i called for warranty, they where very polite just asked me for the model.number and the serial number on machine got 1 back in 2 days and they even paid returned shipping. Great custommer service. Will buy another if something happens to this one. Highly recommended