I'm running the X120e with 4GB ram, 320gb stock HDD and the E350 CPU. It's a great little notebook.
- Linux compatibility may be less than perfect with certain distributions. I don't know what Kernel works the best. I do know that Linux Mint 11 runs quite well and all the hardware worked for me that I use.
- The screen is pretty basic. Color reproduction is alright, but it's a little warm for my liking. Playing with the color calibration helps. Brightness is not like some other Thinkpads. Displays are vastly different from model to model.
- I love the keyboard. It has great feedback and I rarely miss keys. The only thing I can say is push the spacebar more to the center. I find it's sometimes unresponsive.
- Durability is pretty good. It doesn't have the rubberized coating, but other than that it's a pretty tough little notebook. The hinges have a slight amount of play in them, but they are the traditional metal exposed hinges. Just painted black.
- I went with the E350 because it was only $50 more when I bought mine. The only thing I can say, is up the ram to at least 4GB, that will help vastly. The processor isn't really the bottleneck, I think that limited single channel memory and a mechanical hard drive are more the hindrances here. Heat output on the X120e is great, it runs very cool. I can run it for hours on my lap and it doesn't even feel really warm to the touch. Battery life shows this, I can get up to 8 hours on my 6 cell.
- I would get an SSD if you can swing it, but you may be more interested in getting an aftermarket one. You might pay a premium for them to install it and configure it.
- I can't comment on the X121e other than I don't like the rounded corners. I prefer the casing of the X120e, especially for hinge placement. Never liked that behind the back bezel hinge like the Macbooks. No room for ports on the rear.
- I don't really know what else to recommend. If I were buying a new subnotebook, I'd be getting an X120e for myself (if I didn't already have one).
I hope this helps