Intel aren't in trouble... they remain the largest semiconductor manufacturer in the world with twice the revenue of their nearest competitor (samsung)... AMD are not in the top 10 (Meaning that intel's sales were over $30bn while AMD didn't make the $6bn required to get into the top 10). These numbers are for 2004. For comparison purposes, I work for Zetex Semiconductors, and our 2004 sales were $139.3m.
It's cyclic. AMD took the lead from intel with the Athlon. Intel made a few screw ups with the later P3s (mainly in the i820 platform and the whole rambus debacle). Early P4s were poor and their platforms were in disarray with i840, i845, etc making life very complicated with the Memory Translator Hub requirement. i865 and the 800MHz FSB brought intel back to prominence and were very good indeed. With the concentration now on 64 bit, AMD have been in the x86-64 market longer.
AMD seem to have their 64 bit strategy a bit more together, although intel's Core Duo chips are very interesting. With their basis in the Centrino "pentium-m" processor (which itself was more closely related to the P3 than the P4), they overcome the P4's problems with power and low IPC. Don't underestimate the marketing effect of Apple's very public move to these processors (although apple themselves account for only a very small part of the market, people often follow what they do).
The Dell situation is that as long as dell use intel processors exclusively, and in their advertising display the intel branding (and play that annoying plinky tune), intel pick up the tab for ALL of Dell's advertising. Dude!
prior to that i recall we had 1 guy who was sad to see his 166Mhz pentium go because it just performed way over spec. he had autocad 2000 running on it at one point (which seemed to tax our PII 350s pretty badly) and said it was fine.
