I worked in one of Dell's outsourcing partners' call centres (admittedly I left almost 15 years ago), and back then it was the same people manning both consumer and business support lines. Towards the end of 2007 Dell started separating the two segments and that's where the problems started (edit: not sure about the exact date -- processes like that tend to take a while to plan) :
* Dell European consumer division was centralized and controlled from Ireland (IIRC).
* Consumer models like Inspiron and Dimension had a noticable drop in build quality.
* Support agents were forced to adhere to strict scripts during support calls, rather than use their own brains.
* Support agents had to convince a certain percentage of customers to replace parts themselves, rather than getting the on-site service they paid for. Agents not fillin their daily quotas were disciplined.
* Exceptions to the scripts had to be escalated. In many cases, Dell would outright ignore local consumer laws when handling complaints.
I'm sure things might have changed since then. Personally, I'm not taking the chance and will never buy a Dell product again, if I'm given a choice.