So far, I am happy with my Dell E521 and decided to get it for these reasons:
1. Much needed boost in processing power for photo editing (Athlon XP 2200+ to A64x2 5000+)
2. I got it for a great price (~$270 in savings)
3. It included a legal copy of Vista for cheap
4. I got #1-3 for significantly less than I ever could if I would have built it on my own
5. I couldn't re-use parts from existing PCs to save money, as practically everything I have has been rendered obsolete by the wholesale shift of interface standards: PS/2 --> USB, DDR --> DDR2, AGP --> PCIe, PCI --> PCIe, and PATA --> SATA
So far, the Dell-ness of the PC has not presented any significant problems that have marred the user experience. The bloatware really was a minor concern. The biggest issues to date have been with the operating systems and application incompatibility, but this has nothing to do with it being a Dell.
In retrospect, sometimes I do wish that I had built my own PC to be able to use an overclocked C2D for three reasons: (1) I don't think people have been able to extract more processing power from lower end CPUs through overclocking since the Celeron 300A. That makes a C2D setup a relative bargain; (2) I find that even an A64x2 5000+ is not fast enough for painless photo editing; and (3) the C2D is just more efficient in terms of processing speed vs power/heat. I was contemplating getting a 6000+ as a drop-in CPU upgrade, but I would be almost doubling the CPU power consumption and heat generation from 65 W to 125 W!