With SR&ED its possible to get back a substantial amount (like 2/3) of the money you invested into development. Another way of looking at it, is that it's like doing your development at offshore rates, except working with local talent.
In fact, it self-propagates: Fund your initial development, get back a portion via SR&ED, use that toward development, get back a portion via SR&ED etc.
Our start-up has really benefited from this, and frankly I don't understand why any company (big or small) who has an eligible project would not apply for this.
It is actually reasonably easy to find out what CRA is looking for, by attending a CRA public information session or two, and then filling out the paperwork yourself. Consultants "increase the odds of success" purely because they understand what the CRA is looking for -- but it really is not that complicated and can be picked up easily just by going to an info session.
If you can't be bothered to spend the time doing it yourself, then who's to say its not worth giving up 25% of the 2/3 you could get back.