the poster is a bit webby, is that a good way to describe it?
Most posters for gigs need to be versatile in their final output, if you have a full cmyk process and an amazing printer it will look just fine, however most gig promoters don't have that kind of money. The only time I've seen full colour, decent stock, posters is for tour posters with touring bands, it is an expensive part of the promoting process, and most people aren't prepared to spend the money.
What you've got to kinda think about when it comes to gig posters is think about that thing going through a photocopier as your highest priority and then worry about other mediums afterwards. I've made a far amount of posters in my time and only once have a seen a design printed in colour(!!) and that was because it was a custom job for a A1 design. I've got a regular job working for a venue in Cardiff based on the fact that I do good work that photocopies well.
Sorry if this sounds a little rambly.