I've managed to get a G41 and G50 side-by side. The two main external differences is simply that the G50 has a 'regular' Thinkpad power connector (the larger one) and the LCD is much brighter. The G41 is entirely IBM-branded, whereas the G50 is lid-branded IBM Thinkpad whilst the LCD bezel and base is branded Lenovo. The G50 BIOS has also list the 'IBM' name as well as a few less options...
The biggest difference is that the G41 has a Pentium 4 CPU rated at 3.06Ghz, whilst the G50 has a Celeron M running at 1.6Ghz. Is this the performance hit that it seems like on the surface? I mean maybe a Core 2 Duo at 1.6Mhz, with the right OS might somehow compare to a P4, but a Celeron!? Seems like a massive downgrade. But I don't really know much about comparing the two.. Any comments? I do wonder if I could upgrade the CPU to a Core 2....
The IBM G40 was labelled as being made FOR IBM not BY IBM. I think perhaps both of these machines were actually manufactured by Acer or something like that? Funny how that worked with the transition of IBM IP to Lenovo.
Kinda weird that the G4x and G50 machines were intended as desktop replacement machines (like the Multistations and the CL57) but it never had a docking port.
Ideally, I'd like to replace both keyboards with less -shiny ones but they're not exactly common now. The keyboards are the same on the G40, 41 and 50 so you can easily do so.
I've noticed that the CPU heatsink on the G50 is hideous. It uses a triangular shape over the CPU and you screw them down in a particular order. However, 1 is a screw, which screws directly into the motherboard and the other two are more like bolts which screw into 'floating' upside down screws built-in to the motherboard - however the floating screws are so shallow, their threads rarely catch the heatsink so it's almost impossible to screw on. Really bad design.
As an aside, I know someone that fitted a Thinkpad A31's SXGA Flexview panel into the G40 for better colour definition.
Here are some addition pictures I took of quite a high specification G41, which remains IBM-branded, with a 3.33Mhz P4 CPU, 2Gb RAM, DVD and 1400x1050 resolution - a real powerhouse, this IBM-branded Acer design continued in the transition from IBM to Lenovo but was somewhat upended by a mixture of the A-series, Z-series and R-series.