Win 8 is certainly 'different' - the look and feel are more like a phone than a PC (at least until you get it sorted to your own preferred layout).
Any new laptop will be running (at least) Win 7 unless you are prepared to wipe it yourself and go back to XP. Anything that will run on 7 will also work on 8 (at least in my experience), so there is only the look/feel issue to consider.
As regards 'backwards compatibility' I've actually got stuff to run on Win 8 that had been useless since I moved from XP (never did get it to work on 2000 or the horrible Vista).