No. I was really looking forward to Halo Wars, but I played the demo so much that when I got the game I was already bored of it.
I will agree with this point on some level. While the Halo Wars demo ruined the actual game for me, which I STILL haven't played on other then skirmish once, but ODST I think would be different. Because this is the Halo we know and love, by Father Bungie whom we know and love. Not LOTR BFME with warthogs thrown in by out stepmother -blam!- Ensemble. That's a big factor.
I think a local or even online firefight demo would go over much better then the Halo Wars demo because it's A) Co-op, which will always add some re-playability, B) FROM Bungie, and C) Better for a fast 5-6 wave flash that would let you wanting the rest. Halo Wars basically gave you the whole game in 20 minutes.