An effective throughput of 2.1GB/s is still nothing to sneeze at.
Certainly, there is agreement on the fact that the XP is not a workstation platform, simply because its lower memory bandwidth can become saturated while undertaking tasks that require high levels of memory access.
For the rest of us, however, the issue is moot.  Unless you constantly use programs that require high memory bandwidth, the real-world differences in performance are fairly negligable.
The first principle of benchmarking or reviewing components is to run them at maximum workload to see what their limits are.  The same goes for performance car reviews - the magazine takes the car on a closed road and tries to push it hard to see how well it caters to the 5% of people who actually care.  Realistically, you're still going to have to drive at the speed limit (well, I hope you do!) and the performance will only rear its head when you undertake the occasional maximium-workload manouver like quick overtaking or burn-outs at the traffic lights 
 
What does this mean?
That 2600+ you might buy 
might not be as super-funky as the equivalent P4, but it doesn't really matter.  Your life is not going to fall apart when your friend with the new P4 beats you by 1-3% in real use.
AMD still provide the best bang-for-buck processor on the market.  They have the largest number of supporting motherboards and chipsets, and are custom-designed for the person who doesn't want to buy a Compaq.  If you need the extra memory bandwidth, then you should realistically consider what your budget is.  You'd really want 1066 RDRAM because otherwise the increase in cost isn't worthwhile.
I'm not an AMD fanboy.  I don't hate intel.  They seem to have been caught at a little sabotage with the whole bapco thing, but that's normal for any competitive industry (you'd be surprised, but it does happen).  
Shock horror: Most people don't spend the price of a small car on computer parts.  Most people don't overclock either.  And 40% of people still use a GF2MX.  Do these people care about theoretical bandwidth they'll never use?  Hell no.