I have a computer with 512MB of RAM Memory, CPU Intel Celeron 1.60GHz and a 80GB HD. After the new Minecraft update to 1.3.X, Minecraft don't run on my computer any more even on Windows XP and Lubuntu (LXDE/Openbox) and Netbeans 7.2 freezes all the time. So would like to know if Raspberry Pi runs this softwares correctly? Before I buy one.
As you can see on Raspberry Pi FAQ, the real performance of the Raspberry Pi is something like 300 MHz Pentium 2. There is 256 MB RAM installated on both model A and B. Try to compare this parameters to the parameters of your computer.
The reason that Raspberry Pi could smoothly play BlueRay quality videos is in used Videocore 4 GPU which provides Open GL ES 2.0, hardware-accelerated OpenVG, and 1080p30 H.264 high-profile decode. GPU is capable decoding a video encoded by H.264 codec at 40MBits/s.
But overall computing performance is much lower than performance of hardware you have. Raspberry Pi is aimed to completely different usage. Don't buy it if you want to run software that has sometimes problems with performance on 10 times more powerfull hardware.
The system requirements for NetBeans state that it needs minimum of 512 MB of memory to run. Since the Raspberry Pi only has 256 MB of RAM, I would have to guess that there is very little chance of getting Netbeans to run. Especially considering that to run a graphical desktop, you should probably be giving the video processor 32 MB of that memory leaving you with somewhere around 224 MB of RAM available to the system. Perhaps an old Refurb IBM Desktop would better service your needs.
There is now an edition of Minecraft specifically for the Raspberry Pi. It's called Minecraft: Pi Edition. I know this only answers half the question, but I figured I'd leave the information here for future reference.