I honestly haven't looked at Dell hardware for a very long time, since most of the physical stuff we deploy is outside of the US and they have horrible international warranty service. Their low end consumer PCs are garbage and always have been, but I've heard the business lines of desktops, laptops and servers are still halfway decent.
Warning: anecdote from a Winddows admin incoming.
I started working in a Compaq shop. Which became HP, of course.
Then a heterogeneous shop with IBM, Dell and HP.
Then an all-Dell shop.
Then an all-HP shop.
In my experience, all three brands have had generally the same reliability and performance - but the ease of server management (installing drivers and updates, configuring lights-out management and alerts, etc.) and the experience of tech support have been significantly better with Dell.
(Regarding SANs - I've found that EMC is ridiculously fast yet ridiculously cryptic to manage, EQL is ridiculously easy to manage yet struggles on performance and reliability, and new tech like Nimble so far appears to be both very fast and very easy. It'll be very interesting to see what an EMC/Dell merger would produce. I have zero experience with Compellent.)