I like oranges

I also got the Orange Box as well, I already own HL2 and HL2:Ep1 for the PC and my PC is capable of running the game probably reasonably well but I wanted the whole package in one spot (DVD).
Some early comments:
Half Life 2 - is starting to show it's age with the texturing but the gameplay is as good and fun as ever, the lock-on effect for the 360 version takes a bit to get used to, to be honest I sort of wish they removed it for the standard control. The hoverboat portions are a LOT easier with lock on though so I was somewhat happy, I found that part sort of frustrating on the PC.
I haven't gotten into EP1 and EP2 yet, I'm playing the game from the start to refresh my memory (and collect achievements)
Portal is awesome, very addictive. It's one of those games where you say "just one more level" and 40 minutes later you're still playing. I did encounter an odd bug here where my savegame was corrupt. Not a big deal but I was worried I'd have to start over. Thankfully I just had to restart the level.
Team Fortress 2 is great, though I only have one match in it so far. It's really well done, the graphics are perfect really. I'm a bit disappointed that there are so few maps and I never did find a class I was any good with but eventually I'll spend more time in here. I'm a bit worried that people will get bored of it and finding matches in here may get difficult if people go back to Halo or other Live titles.