(Looks like jtrops beat me to it, but here’s my $0.02 to add to it.)
Hi Doug,
If you do a “Tag Search” for “brakes” you’ll find lots of threads discussing the questions you raise. See, for instance:
Basically, if you are new to riding you’re probably better off waiting to get brakes on your 29er. When I started riding muni I rode my N24 for a couple of years before I felt I really might be able to make use of a brake. Maybe you are at this point now too. Like you, I started using a brake once I started riding a larger wheel (KH29). 
Like many others, I started out with refurbished Magura rim brakes that I bought from Brycer :D, after I bought the uni. (Check out Brycer’s current selection in this thread: Magura Green Frog limited edition HS33 brakes, new and used)
Brakes really only come in handy when you are riding very steep descents on trails, or long steep descents on roads. On trails they allow for greater control by slowing things down and evening out the power cycle of the pedals. On long descents on both roads & trails brakes give your leg muscles and knees a brake from having to keep substantial pressure on your pedals throughout the pedal cycle, particularly during the up-stroke, when the pedals are coming up behind you. :o
Of course, if you are shopping for 29ers now and can afford one with a disk brake, it will be there for the times when you need it in the future. That is, unless the brake lever gets demolished by a rock during a UPD before you are ready to use it. 
This is another reason brakes aren’t recommended for brand new riders – the more UPDs one has, the more likely the brakes will be destroyed during one of them. Better to ride without brakes until the UPD frequency is reduced. 
I hope this helps. You’ll find many more opinions in the other threads devoted to this very topic.
Happy trails,
UPD in Utah