Mac's can't touch windows in the HTPC realm.
No cable card.
No blu-ray.
No HD audio.
No custom cases...I need to hold at least 6-8tb. Mac Pro maxes at 4 hdd's. I would prefer a case with at least 6. 5-6 for storage and 1 for OS.
Horrible pricing for Mac Pro. (At $2500, it comes standard with 3gb of ram...and apple delusionaly charges an extra $225 for 3gb....oh geee, what a great deal!).
That's a massive deal killer.
Also, at least in the legal world...there are so many programs that are windows only.
Bootcamp works, but that is cheating...you're only using Mac Hardware then.
I use my Macbook everyday for school and casual use...probably always will. However, for my HTPC uses and work, windows forever since Job's said Apple would never adopt Blu-ray.
And yes, I have over 400 HD movies on my HTPC.