I'm a Comodo firewall user and there are a few negatives but the positives in my experience outweigh the negatives.
What I like about Comodo firewall:
1)It gets Tru Stealth at Sheilds Up.
2)It's easy to use.
3)The developer has been responsive to complaints/suggestions.A good example of this was the high resource issue in the early version of CPF.Comodo lowered RAM usage in a short period of time.
4)The program is also configurable to a certain extent.
These observations are based on version 2.4.
Version 3 promises to be a much different beast.