I've been using Comodo for Vista 64 for about 1 month (along with AVAST AV) and I've been relatively happy.
I haven't much noticed the impact of their recent minor version upgrade, but then again I haven't looked for changes in any detail either.
I turned off the Vista Firewall and MS Defender.
I've seen Comodo block a lot of incoming / outgoing traffic attempts from both unknown / 3rd party traffic and applications, as well as ask about blocking/allowing even several known/"safe" applications (vista components, IE, whatever). In this context that's a good thing that assures me it seems to be doing its job in securing the system and allowing me to be as restrictive or permissive as I like about what to allow. I'm sure that most people would just let it be pretty permissive by default and that'd be OK for them.
If anything the greatest annoyance for me about it is that when I tell it to remember to ask, block, or allow something (say by application not by port/IP) then it's not so easy to track what has been allowed / denied in some cases. So if you want to go back and look at all allowed / denied traffic / application attempts you can't totally generally do that. It's hard to describe because there are logs you can enable of allowed/blocked traffic, though it's just not quite as general as it could be about letting you choose what to log in what detail etc.
Then again it's better than anything else I've seen except for things like UNIX firewalls where you program them at a super low level and can log *anything*.