Pros: Ergonomic, simple, great LEDs
Cons: Small for my hand (8 inches or 17.5 cm), limited LED settings
Cons: This product is great for the average hand. My hand is slightly to big and I have some difficulty completely palming the mouse. My hand is approximately 8 inches (17.5 cm) and if I were to properly grip this mouse in a palm fashion, I would have 1 inch (3 cm) hanging off the end of the mouse. The color customization allows you to put any color you would like using a color wheel in the software, but there is a lack of effect customization as you are limited to breathing, static, and cycling effects. This does however simplify the process if you just want a matching mouse.
Other Thoughts: Overall this far outperforms any mouse I have previously used and I am thoroughly enjoying its functionality. My only complaint is it could be bigger. If Razer could make a Deathadder-XL for the massive hands that want to truly palm a mouse, I would be sold. My final notes are about the warranty and software. Warranties are easy to register and track by registering a Razer account, and the Razer Synapse 2.0 software registers all your Razer products with no issues. My warranty expires in 2016 and I bought the mouse in 2014 so there is a solid 3 year warranty if you suffer cases of nerd rage. Razer Synapse 2.0 also makes setting up your mouse extremely simple with useful functions like macros, DPI adjusting, liftoff distance, and even sensitivity stages for whatever that can be used for. There is also a "Stats" tab to show your mouse clicks and movements in game projected by heat maps. This isn't that useful unless you really want to dive in and analyze how straight your mouse moves.
Side note: The Razer Synapse 2.0 software conflicts with OBS. You will need to close the software to use OBS.
EDIT- Side note #2: The Deathadder doesn't function when using the Windows 7 installer. I was installing Windows on an SSD and had to pull out a random wired mouse. Could be the USB 3 drivers were not installed yet though. The mouse worked immediately when I got passed the installation process for Windows. Correction- The issue did end up being the fact that I was plugged into a USB 3 port. Just remember to use a normal USB port if you are performing an installation of Windows or something.
EDIT #2- After a year or so of using this mouse, the cable sleeving has frayed and split where it rubs against my desk. This doesn't bother me and it is probably due to how sharp the edges of my desk are. I have changed to a Razer Goliathus Extended (Control) for my mouse mat, and I do enjoy the feel of a Deathadder on that mat a lot more as seen here in my review.
EDIT #3- After average use for around one and a half years, the mouse quality has suffered significantly. The rubberized coating is starting to remove itself on the clicks. The braided cable collects and holds dust and the mouse feels slippery. I can only imagine how quickly this would happen for a constant user. I will resort to something else once I have serious problems with the mouse. Func was an option until they were acquired by Fnatic and all their equipment was discontinued.