I use Elite Software's "CHVAC" program. I have used Carrier's HAP program and it is far more difficult to use. CHVAC is superior to any other load calculation program in my opinion. It is easy, straightforward, accurate, and there is free technical support.
The only downside is that CHVAC is not as widely used probably. I also use RHVAC for residential.
One thing they just added to CHVAC is the functionality to choose any commercial equipment such as cooking equipment from a drop down list. Very very nice feature.