I have a T40, and have thought about buying a used T43, but have seen on ebay these models at very reasonable cost and they are new, is there any things that are missing on these models comparing to a model like the T43? Cpu performance? Or are they even better then old models like T43?

Thanks in advanced.

Naturally, the performance is gonna be better on any newer model compared to an older model. Faster CPU, more/faster RAM, bigger/faster hard drives, better WiFi, etc.

SL is supposedly lacking in build quality (plastics, fit-n-finish, ruggedness) compared to the T-series, although still feels quite durable. It is also missing some traditional Thinkpad features, such as docking station support, Thinklight, removable optical drive, etc, but also has quite a few other features which an old model such as T43 does not have, such as Firewire, more USB ports, built-in camera (on some models), HDMI output.

On the other hand, T43 has a PC Card slot, which SL doesn't have (they have only ExpressCard), and parallel/S-video ports, which are no longer present on any modern Thinkpads.

In your particular case, T43 might have an additional advantage of being compatible with all your T40 accessories, if you have any (such as power adapters, docking stations, batteries).

As the owner of a thinkpad sl500 for a little over 2 months now, I can say that I am pretty happy with the build quality. I had a 600 as my first thinkpad, which still takes the prize as most sturdy. My t23 was (is) pretty flimsy by any standards, but it was also bought used so i do not know what kind of abuse it was put through. As far as build quality, it's excellent for the price, although keyboard flexes just a little bit. No motherboard/case flex to speak of though.

I went from a T23 to a T40 to an R61i to an SL500. The SL500 is not a T series (in terms of build quality and being light), but its nice. The build quality is still better than most laptops, feels nice, and for me it has newer features with the red trackpoint. I used a dell latitude for a bit with a pointing stick, wow I will never make that same mistake. The keyboards and rugged feel of a thinkpad is what keeps me coming back.