The 32DDR is pretty much the same thing as all the rest of the Radeons except for differences in memory, video in/video out (VIVO), and TV tuner support. I have this card and it works great, like any other Radeon.
As compared to a GeForce 2, the Radeon doesn't have quite the 3D speed of the GF2, but it is relatively close. The Radeon on the other hand, is thought to produce a better looking 3D image than the GF2. The Radeon excels in 32-bit rendering speed and has a more complete DX8 feature set than the GF2, though not nearly as complete as the GF3 or the upcoming Radeon 2.
Why I got the Radeon was for its superior 2D image quality and great DVD playback. The Radeon is far and above the "run of the mill" GF2 in these respects.
As for how long this card will last--it all depends. I intend to be able to use the Radeon for at least another year, though 3D gaming is not all that important to me.
With the Sony g520 monitor the Radeon will work great. It has a 350 MHz RAMDAC and supports very high resolutions.
I would suggest however, that you look into getting a 64 DDR VIVO Radeon instead of the 32DDR. The price difference betweem the two is becoming increasingly small. Even better, if you are looking for TV tuner support, you could get the 32 DDR All-in Wonder Radeon (AIW Radeon) for about $40 more than the 32DDR.