Professional chainsaws aren't made for everyone.
If you head to work with a lunch pail in one hand and a chainsaw in the other, they're for you.
These chainsaws are designed to cut all day, everyday.
There are a few things that separate professional grade chainsaws from other saws:
Top Handle

Prosumer chainsaws introduce a new style to the mix - top handle models. These chainsaws are usually smaller than rear handle models and are easier to operate.
Due to the handle position and light-weight, top handle chainsaws are used to cut branches and tree limbs. These are popular with folks cutting on ladders and in trees, or other situations where you need to cut on a downwards angle.
Balanced Design

Look for a chainsaw with a balanced body design. A long, narrow body layout with the engine situated inline, directly behind the cutting bar is the most balanced style.
This is an important future for folks who use their chainsaws for extended periods of time. The balanced body is easier to hold evenly, even after an hour of cutting.
Commercial Warranty

Professional chainsaws are sold with two year commercial-use warranties. This is especially important when you're regularly using your chainsaw for several hours at a time.
Two year professional warranties on power equipment are not easy to find, considering the demands put on them by their owners and operators. This should provide peace of mind while using your chainsaw in extreme settings.