The biggest difference you’ll notice is the handling. A triathlon bike wants to cruise, in a straight line and on the flat. If you ask it to do things outside of these parameters, such as accelerate fast, corner nimbly or climb, it’ll feel slow, cumbersome and a bit barge-like compared to your road bike. That said, the more time you spend training on your triathlon bike, the more you’ll get used to its handling quirks and the less you’ll notice them.
The next difference is obviously the riding position. Your centre of gravity is further forward over the front wheel and, with elbows, arms and hands narrow, it can sometimes feel a bit twitchy. However, if your position has been correctly determined and again if you invest time riding in it, and not just on the turbo, it’ll become second nature.
Finally, the positions of your brakes and shifters. Electronic shifters with satellite buttons negate this but, if you’re on mechanical gears, you do have to plan a bit ahead going into climbs or turns, especially if you’ll be getting out of the saddle. If you’re on your tri-bars (aero bars), your brakes aren’t to hand, so this needs to be considered too. Again, though, practice makes perfect so just put in the training miles on your tri bike.