My experience with Viewsonic differs. I love the VP series and have used them for the past 5 years. I have 8 of them and only 1 had a problem after 2 years of use. They have an excellent 3 year warranty and the monitor was fixed and shipped back to me.
I have 3 more Viewsonics in Chicago for when I go visit my fiancee. I also bought my brother and sister the same monitors (VP201b) for Christmas last year.
I saw the 20" widescreen dell on sale with a coupon for less than $400 earlier on the year and the price was just too good to pass up. It's fine for what I use it for...just for briefing.com or other news sites...and I love that it has PIP so I can run CNBC in a small window. I don't think the picture quality of the Dell is as good as the VPs...and I can't use the resolution for my charts which I set up for 1600x1200. But it works fine for what I use it for.
I'm thinking about getting the 24" Dell early next year when I upgrade my computer. I love my Viewsonics...but the Dells are starting to get too cheap relative to other monitors to justify paying a 30% or higher premium.