That should would be amazing! I love the idea of extinct creatures returning to walk among us, and it's very sad to think of all the species that died away which we'll never get to see again... So reviving pre-historic animals like the wooly mammoth would be very exciting.
I guess the only downside is that, if science did progress to that level, there could be an argument that we'd be "messing with natural order".
The repercussions of this could be pretty serious.
What starts of as a neat idea (for example creating a theme park full of real-life dinosaurs) could end pretty badly if we're not careful.
Apart from the threat of T-Rexes running around eating people up, there's also the danger that our current ecosystem might be badly affected.
Brining back extinct species would create more competition for food and other resources, it could lead to crop shortages or other problems that would directly affect humans and wildlife...
So to sum up, yes I'd pay to see a wooly mammoth at the zoo, but if things go badly don't blame me!