How much do the programming functions on the higher end radios help a casual racer? Is it worth spending the money to get adjustments like expo, or for the casual racer is a basic 3 channel good enough?

Many features go unused, not only by the casual racer but also by the pros. Some are nice to have though, but generally the higher end radios are chosen for their quality, speed, ergonomics, etc. nt the number of features or channels (not with our go-fast-cars anyway). Totally different stories with other types of RC models (planes, helicopters or trucks, excavators with dozens of functions)

That is a personal thing. When I got an advanced transmitter I played with many functions like logarithmic steer but at the end I ended up with all neutral what gave me the best feeling. But there are others who like to use such adjustments.

Extra functions like endpoint adjustments, subtrims, brake power and D/R are always nice to have.

Expo is used by a lot of people, and is available on some pretty cheap radios - for example the Futaba 3PV. On the other hand, I use an M17 and pretty much just stick with EPA/Dual rate and trim as my only adjustments.

Most of the pro level drivers in my area have gone away from using expo because it creates a snap oversteer problem when the expo fades out and abruptly goes to full lock in mid corner.

Instead they will use steering speed and throttle speed to soften the control. Many ESC's also come with new features called "Frequency" rates which are similar to speed settings. These are linear which don't create snap oversteer like expo does.

As track conditions change, you'll see pro drivers adjust the speed settings, brake strength, etc when tuning during warmup before the race begins.

A lot of it also depends on the class you are racing. On-road carpet will use Expo on steering as well as dual rate, especially in 1/12. Off-road, it is nice to have dual rates for throttle and brake split and key assignable so that you can adjust your brakes to suit track conditions while on the driver's stand. I also use expo on throttle for 2wd buggy on dirt. Servo speed is nice, as well, to calm down the super fast servos we use now.

The other thing the higher end radios have that some mid-range or lower radios don't are the ability to adjust the ergonomics of the radio. Everything from switching to a left-hand steering wheel to adjusting the size and feel of the throttle trigger.

But if budget is a concern, the Mid-range radios will have pretty much all of the programming features and speed that a top of the line radio will have, but they won't have all the ergonomic adjustments. So if you don't mind that, something like the MT-5 is a great radio.

The main difference why racers buy such a high end transmitter is because the speed. Most simple transmitters just transmit their servo info with a 50Hz framerate, any decent transmitter can go up to 333Hz (digital servo limits) and the high end transmitters go much higher in frame speed that will give a better feeling and more precice steering with the car.

I mainly use expo (negative) and servo speed. Most go unused, but those ones are key. I absolutely don't regret buying an M17, but an MT44 or 4PM would do everything I need to.

Servo Speed is one of my most commonly used and adjusted settings. You can take a lot of twitch out of the car, and keep a lot of positive steering feel, just by slowing down the transit speed of the servo. All of the resolution and response time is left the same, its just not slamming the servo back and forth at full tilt boogie. So things like "the jitters" and nerves dont translate to the car on the track.