If it were me I would say I don't know why it would have a problem. Testing the laptop with an Ubuntu LiveCD will give you an answer quickly. If you can test it in the place where you are buying the laptop great. If not, when it arrives test the laptop.

But there are a couple of issues still present (At least in 12.04).I have also added some links of some old posts and bugs (That affected 11.04 and 11.10) that you might want to check and the ones that affect 12.04:

http://ubuntuforums.org/showthread.php?t=1889596&page=6

(11.04 and 11.10 users. most problems were hardware problems and not Ubuntu)

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/974455

(Suggest to do a BIOS Firmware upgrade)

http://support.lenovo.com/en_US/research/hints-or-tips/detail.page?&DocID=HT073063

(BIOS upgrade)

http://www.linlap.com/lenovo_ideapad_u300s

(Users confirming problem with 12.04 (And other distros like Fedora)

In general there are 3 problems detected:

• Suspend/Resume does not work correctly.
  
  (There is a fix for this already)




• Touchpad functionality is not working properly. Recognized as a generic PS/2 mouse.
  
  (Fix for this is on it's way)




• Some keys like T or any of the Arrow keys do not work correctly. Although this problem is more related to a hardware problem by many users. There is even some that have fixed the problem by either upgrading their BIOS or draining the battery completely (Again, more related to hardware than a system since it also happens on Windows).

I would recommend to either, wait for 13.04 or apply 12.10. Any of this 2 will have less probability to have any of this 3 bugs. Also verify the keys when the laptop arrives just to check that all keys are working correctly. Then simply test Ubuntu using the LiveCD or LiveUSB. Will save you the trouble of installing it and getting any error (If any appear in your case. Remember the problems mentioned do not happen to all users, only some).

For some additional information here are 2 positive links:

Stuart Langridge testing the Lenovo U300s

(Several tips by Stuart)

Ubuntu Friendly with the Lenovo U310

(Could not find the U300s)