Thank you for ideas.
Now I start thinking about something stronger (to work with 2 or 3 virtual machines at one time, so 8 - 16 GB of RAM).
From your comments looks like I need to look for ThinkPads T or ... ThinkPads X ... Not very big choice...
If you want to be running 2 or 3 VM's at the same time from a laptop, you need to get a decent hard drive, otherwise you won't be able to do anything big on them, except one at a time. Laptops usually come with 5400 RPM drives, which for running multiple VM's is less than ideal.
If you can afford it, put an SSD in the laptop, or a 7200RPM hard drive (which will also eat away the battery life faster than an 5400RPM one). Alternatively, I think the latest T-series have eSata, so you can get an external HDD and put all the VM's on there.
In my own experience, I just love the Lenovo T- and X-series. Our office has been using them for many many years. We hardly have any problems with them at all. We also have a lot of staff travelling extensively and they all are very happy with the laptops. Last year I bought my own T420s for personal use. Came with 8GB and I put in a 256GB SSD.