Well, it depends on what your going to do the majority of the time. Flexview with it's IPS screen is absolutely fabulous; depth of color is incredible, color reproduction and accuracy is also very very good, and best of all, it has that nice wide viewing angle.....however it is not without its faults. It generates all these images *slightly* slower (we're talking a difference of 5 and maybe up to 20 ms delay in refresh rate). This screen is excellent for photoshop, premiere, autocad, or any industrial design or photo/video applications. I hear that it is not too great for gaming, do to the slower refresh rate.
Actually the 2379-DXU model was one that I was looking at. However in the end, I decided that it wasn't the model that I really wanted, since 15" flexview screen would add more weight and make the unit much thicker (1.2" to 1.4" thick), and I need a more portable unit.
It all depends on what you want to get out of your thinkpad. It has to fit what you want it to do. The M6n is a fine alternative, however it isn't without its faults too (i've seen more problems regarding the M6n than the T-series).
I hope this helps. Ultimately, it is your decision. lol, i tell people that they really won't be happy with any other laptop except for an IBM or T-series. It really is worth saving up for.
I wish you the best.