In my idea, it all depends. Lot's of other factors come into the play:
- Does your team have a dedicated tester?
- Are you in a hurry of delivering a buggy demo to the client?
- Do you mind the first release not to have bugs?
- etc. etc.
I mean, while general guidelines exist, no prescription can be made for all teams around the globe.
Yes, of course testing and all concepts related to it would increase the quality of your product in a considerable way. Concepts like regression testing, unit testing, coded UI testing, integrity tests, security tests, performance tests, and all of'em make your software to become a first-class citizen to compete in the market. But that's only the academic view.
The practical view is however sometimes a little different. If you really need a demo, then write more code, and test less.
If you have a dedicated tester, then let him take the responsibility of testing. Collaborate, work together, but you spend more time developing and less time testing.
Also try to reuse tests through writing automated tests and getting far from manual testing.
As the last suggestion, I recommend that you reduce the features, because as a general rule:
Less robust features outweigh more buggy features.