I don't think anyone can give a general statement like "2gb is wasteful" or "2gb is useful". A quick test to see if you will even notice a difference with extra memory is to open task manager, go to the Performance tab and look at the Commit Charge Peak value after you've used your machine for a while. If, for example, it never peaks above 1gb, then you don't need more than 1gb. Run intensive programs, etc etc, to see where you will peak.
I use my laptop mainly for work, and find in an average work day I peak around 1.5gb. The highest I've seen it so far was at around 1.7gb. For me, 2gb made a big difference - I could turn off the pagefile, and find I never bottleneck due to disk access now.
Now, is the time saved because of additional ram worth the expense? This is a tough question, and is different for anyone based on budget, tolerance for waiting, etc etc. For me, work paid for the memory upgrade so it was a no brainer. For others, the cost of a 1gb stick may be too much to pay for a few seconds/minutes savings each day in wait time. But for me personally, even if work didn't pay, I'd do the upgrade. There were time's I've literally waited 5 minutes or more when switching between applications when I was at 512megs of ram (I normally run Virtual PC, Oracle, and VS.NET all the time, with other applications on the side). Now, as I said, I don't notice any wait times.