RobotC is my preferred programming environment when I need more power than can be found in NXT-G. I always recommend it, but the only real drawback I can say is that they don’t support Bluetooth communications between more than 2 NXTs. I am getting ready to download and install it, so I can’t really speak too much about the upgrade. In the past I have been pretty happy with updates, so moving up to 2.0 should be pretty easy and rewarding.
The upgrade can be done through this link.
From the RobotC website.
ROBOTC, a C-Based programming language for robotics
ROBOTC is the premiere language for educational robotics. It is a C Programming Language with an Easy-to-Use Development environment. It supports several different robotics platforms, including popular platforms such as the LEGO MINDSTORMS NXT and Innovation FIRST VEX. Download its blazing fast, High Performance Firmware to your robot. Using its Interactive Run-Time Debugger, you can easily pinpoint the problems in your programs. Try it out today by going to the Downloads section and choosing your platform.