They're pretty damn cheap now, right around 20-25 bucks, and Shenmue looks like it's going for 15-20 dollars online. I do not own a NES, SNES, Genesis or anything, simply because a lot of those games are available for download, or have been rereleased. 
 
Shenmue has not been made available, as of yet, and it interests me greatly.
 
Do you think $40 is a good deal for a Dreamcast and a copy of Shenmue?

I love Shenmue, but $40 is a bit much. However, if you were planning on playing other Dreamcast games as well, then I would say go for it.  
 
Keep in mind though, it's only a matter of time before Dreamcast games will be available for download. 

I say No because I honestly don't see a point of buying an old and obsolete product that you have no sentimental value for. It's kinda like buying an 8-track. Sure you could listen to old music but most of that music has been re-released and is better quality(something that will probably or already has happened with most Dreamcast games) .

Friend of mine bought a dreamcast this week and we played a hell of a lot of powerstones if you're into that.

Always buy a Dreamcast.

For $25 I'd buy a Dreamcast just to have one, even if would never use it.

If you're really interested in this game I say go for it. It's not the end of the world if it doesn't live up to your expectations.

Yes, there are tons of arcadie games on the Dreamcast. Would love me some Zombie Revenge right about now.  It's an amazing system and Jazzycola has no soul.

Dreamcast was probably my favorite console. I wish I hadn't traded in my games many moons ago.

Buy a Dreamcast, but not for Shenmue.

@ajamafalous said:

Always buy a Dreamcast.

i have been debating buying one myself.

being a Nintendo fanboy growing up, i never touched Sega stuff. Now i kinda want to see what the older systems (Saturn, Dreamcast) had to offer.

If you are only going to buy one game for it I'd say don't buy it.

Should you buy a Dreamcast? Absolutely; it's an awesome system with a lot of great, bizarre games. It was kind of the last real console that fully embraced the weird side of Japanese game development. However, should you buy a Dreamcast just for Shenmue? Absolutely not. The game was ambitious for its time, but it's boring as hell and little of its ambition is appreciable today.

40$ for Shenmue and a DC is a good deal. In retail stores, I see Dreamcasts and copies of Shenmue for 50$ each. Of course, a brick and mortar used games store will always mark-up when it comes to slightly rarer products.

Regardless of Shenmue though, you should get a dreamcast. Great little piece of recent gaming history, an interesting failure to be sure.