Hahaha...
Yeah I am a game programmer too. Been in the industry for almost 12 years now. I agree that porting from the XBox to the PC is going to be failry easy for the "Team" that is going to be doing this (no it won't be the same group of people that put together Counter Strike but you can be rest assured that Randy will probably take a gander at it from time to time).
The main problem with this... and perhaps I am speaking for too many people... you see...there is this thing called...finishing... you know... the game? While probably there are still some PC users out there contemplating purchasing an XBox instead of spending the same amount of money on a Geforce4 video card. I personally think would be stupid to do seeing that I dropped $500 on it and found out that Microsoft only supports a 3 month warranty on its product. If your XBox breaks after 3 months... oops...too bad... so sad... Microsoft wants $127.00 to repair it and you get to pay for shipping and handling too.
Besides all that going against the XBox and the number of users out there who will still be purchasing and XBox over a PC upgrade, I think you will still probably be able to sell around 300K to 425K units and that is if the porting team gets it out before Doom III...otherwise... you go to the store... see Doom III on the shelf... see Halo...the XBox to PC port game on the shelf... which one ya gonna buy? You gonna take Halo over DOOM III?!
I don't think so. The average consumer purchases 3 to 4 titles a year. This would be one of the 3-4 titles. The average consumer doesn't purchase more than one title every 2.5 to 3 months... this means sales for Halo could be scattered.
Personally... I know for a fact that the Halo code base is a whacked out hack job in MANY places and its core engine is going to have to be modified in order to make Halo even a hair remotely fun to play online (seeing that it is right now <Xbox version> peer to peer). Don't even forget all of the specialty code and methods used to take advantage of the XBox (not that there won't be some fairly close if not almost identical D3D8 method calls to replace them.
In the end... I think everyone fighting out here about this stupid title needs to sit back and wait. It is going to be (my estimate being a semi-veteran in the industry) about 9 to 14 months before you see the product...and that is if everything goes fairly well for the team.
You also have to realize the team doing this port is a piece meal team that is being brought together from various different companies. This means that many/some of the team members have never worked with each other... I also know that many of the people are coming from Terminal Reality... and if you look at the titles and quality of products falling out that door mixed with the new team syndrom and the already distant release date for the product.
I am sad to say that it will get done and money will be spent doing it. I will bet that Microsoft gets their $$ out of the deal and the new team will be left standing with nothing more than yet another notch on their belt and a semi-decent salary to boot. I dare to wonder how they will feel if they have visions massive unit sale volumes.
Halo is Halo... great title... great team who put it together. Gearbox is a fantastic company and will do their best to put it out as quickly and best they can. I just think the odds are stacked against them so if you are waiting for Halo to come out on the PC... just go rent an XBox for a week and Halo and play it now. It will save you time and money.