Based on my experiences: Dell's technical support's quality varies drastically from the contact method used. I've only called Dell a few times because I just can't deal with the wait times and the accents of some of the techs, and they often ask you to go through a series of basic, repetitive steps, even if you say you've been through them. When my Axim (PDA) went defective, no amount of soft or hard resets would fix the problems it was facing, and I made that clear to the tech I was talking to. What'd he tell me to do? A soft reset. And then a hard reset.
Dell's live chat is a small improvement over their phone techs, as you don't have to deal with accents, and the wait times are usually shorter. However, they usually go through the same process phone techs go through.
Now, I always e-mail technical support. The last problem I had was my left speaker on my E1705 going bad, making weird noises, etc. I e-mailed Dell, saying that I'd checked all the possible software aspects of the problem, and narrowed it down to the speaker being defective, and also added that I was confident in disassembling my notebook, as I've done it several times already. I received a response within a few hours, saying that a new set of speakers had been shipped directly to me, instead of a tech, and that was it. Out of all the times I've e-mailed technical support, I've never had someone computer illiterate attempt to hold my hand through basic diagnostic processes. They've always been polite, helpful, and efficient.
I don't know if I've just been lucky with e-mails, but if Dell's technicians manning the phone lines and live chats were of the caliber of the techs I've been e-mailing, then Dell's customer service would be damn near top notch, in my opinion.
EDIT: e-mailing has the added bonus of you choosing which department your email goes to, thereby avoiding misdirections.