This I DO know... I used to own the exact card you have, well not EXACT but I did own a GeFoce 2MX 400. And there is a HUGE difference, forget running games at barely standable Res's and mediocre detail, with crappy Frames Per Second. You'll go from running games "smoothly" to "great" not great like GF4ti great, but certainly a whole hell of alot better then a GF2mx that's for sure...
upgrading from a gf2 mx to a gf4 mx is NOT worth it. the gf4 mx's have the same features that gf2's have. a gf2 TI is the same speed as an mx 440 and about half the price. seriously. if you're happy with your card, stick with it. if you're itching to upgrade, get a gf4 TI 4200. you can get them for about $130 now. stay away from anything "mx".
I own BOTH cards he/she's talking about and going from a GF2mx to a GF4mx DOES MAKE A HUGE DIFFERENCE! Is it a GF4ti no, but that doesn't mean he shouldn't even consider a GF4mx, he/she can get a GF4mx for half the price of a GF4ti 4200.
I went from playing Counterstrike at barely 99fps dropping all the way to 30-40fps pretty much when ANYTHING action oriented happend; to now playing at 99-100fps pretty much ALL THE TIME only dropping to never less the 60-70fps and that's for usually a second or two!
I hate to just come out and say you're wrong but... YOU'RE WRONG! If he/she doesn't have over 100bux to spend like alot of younger students can't then the GF4mx is a great buy... Take it from me I OWN BOTH FRIGGIN CARDS!
Should he/she just wait until the GeForce5's come out and get a GF4ti then, that's their call. But Octupus trust me if you want a very good/quick fix to your GF2 situation, take it from someone who was in your shoes, get a GF4mx now and save up for a GeForce5 later...
--btw-- my system specs are a P3 1GIG with 512SDRAM, so even with my beast of a system it made a BIG BIG BIG differnce in pretty much every game I own... But hey if you got extra cash to burn, then I would say sure get a GF4ti that's a no brainer; but I doubt you would've even considerd a GF4mx if you had enough cash for a TI, right?
Back when GeForce 4 MX's first came out... and I was on a budget, I bought a GF4 MX 420 to replace a GeForce 2 MX 400, needless to say it went back to the store after I experienced no difference what so ever. At the time that was on an 800mhz system.
Now I run an ATI Radeon 9000 Pro which is in the same price range as the GF 4 MX's... and my 3D Mark score was 2.5 times higher then with the GF2 MX 400.