I currently have a desktop and have never really been into Laptops. However I like the idea that I can sit in the lounge on the Laptop rather than having to got into the office to use the PC, but surley desktops are much better than a laptop?
On a £ for £ basis you will almost always have more power and storage available with a desktop. If you need more memory or storage later in the life of PC it is always easier and cheaper than with a laptop. Having said that, if you prefer to sit in the lounge and compete with the TV and the wife talking while you try to work, get a laptop. Don't forget to get a laptop support tray that will allow air circulation under the laptop while using it. Modern laptops generate quite a lot of heat and do not like sitting directly on your lap, unlike the wife, if you're lucky.
We have both, a desktop and a laptop and we find that more and more we use only the laptop because as you say it is very convenient if all you are doing is surfing, emailing or writing the odd document. And here is where we find the laptop an inconvenience because documents often need printing out (as do some internet pages). Our printer because of its size and all the paper etc that goes with it needs to be in the study and it is not wireless, so the desktop needs to be powered up before we can print with the laptop. The alternative of taking the laptop into the study, unplugging the printer from the desktop, plugging it into the laptop defeats the object. So our next major purchase will be a wireless all in one printer.... and the desktop will become just a backup for the laptop.