While Intel may have the upper-hand in pure performance at the high end (Nehalem), it comes at a huge price: new motherboard/chipset, new CPU(s), new RAM. The "upgrade" path is (as is usual with Intel) to buy all new hardware.
AMD may not have the fastest CPU architecture out there, but it's not horrible either. When it comes to performance/watt, price/watt and other similar metrics, AMD is doing quite nicely. They also have a very nice upgrade path. You can use Phenom IIs in AM2 or AM3 motherboards, you can use them with DDR2 or DDR3 RAM. IOW, you can actually upgrade the hardware as opposed to just replacing it.
AMD also has an easier to understand model numbering scheme, and it's very easy to figure out which CPU features are supported by which CPUs. It's next to impossible to know, just by the model numbers, which Intel CPU is better than which other Intel CPU (especially when it comes to CPU features like Intel VT). I swear, Intel just rolls a bunch of ten-sided dice and uses that for the model numbers.
Until you can buy a Nehalem-based server with 2x quad-core CPUs, 8 GB of RAM, 4-port gigabit NIC, 2 RAID controllers, 24 SATA harddrives, and redundant PSU in a hot-swappable rackmount case for ~$10,000 CDN, AMD has nothing to worry about.
At least where we are.
Same for desktops. Until they have a box equivalent to ours (onboard nVidia graphics, gigabit NIC, 2+ GHz CPU, 1 GB RAM, onboard sound, etc) for < $250 CDN, we'll continue buying AMD.
So, no, we're definitely not worried about AMD.