HyperZ will keep the RADEON from suffering near as large of a performance hit as the MX will suffer, as polygon counts rise, etc., and this has been proven in countless tests. The RADEON will stay way ahead. Plus, remember the RADEON is much more powerful in 32-bit to begin with, and then will suffer much less of a performance hit .... so, just do the math.
Also, DirectX-8 comes out in 1-2 weeks, and many games coming soon WILL be using the RADEON'S special features. This is confirmed.
So the (future features don't matter) argument is simply not true.
And if you plan on playing at above 1024 x 768 (which I do, 1280 x 1024 x 32-bit), the MX simply can't keep up. Really, the 32MB DDR RADEON is a significant step up from the MX in every way. (32-bit performance, features, Directx-8 support, better image quality, DVD playback, etc.) Like I said, it's a no brainer if you compare the two.
But, if you have a smaller monitor, and only play at 1024 x 768 and 16-bit color, then the MX will definately keep you happy for a while, so you can just stick with it untill the next generation cards out, but plan on spending more money too.
Seriously though, if you can get the 32MB DDR RADEON for $150, you are looking at one of the best values EVER in video cards.