First of all i don't agree 100% with this. My experience is that the IOGear GUC232A is more reliable and that's based on 6 installers plus a few reps during training. If you spend some time searching on this board you will also find some people who bought the keyspan with poor results, while some have had success. I'm sure alot has to do with user error in the setup but that's a variable i can't predict.
But why don't you just do it right and get a serial pcmcia card for your laptop if you have the slot available. Here is the Quatech one I have from Sewell direct...works like a champ and then if you want to get into programming for systems like amx or crestron you are good to go as you will probably find that the usb adaptor will not work for them.
[Link: sewelldirect.com]