First off, the columnist starts off with "Laptop beats Tablet", and then proceeds to list limitations of the iPad; one particular tablet. Some of those limitations (iTunes, replaceable battery, no multitasking) are not issues on other tablets. So, I think I consider these to be marginal arguments against tablets.
Next, the guy lists the advantages of a laptop (ports, storage, keyboard, DVD player/burner). Well, these are all things available (in even more abundance) on a desktop PC. So, I could make that same argument that my desktop beats his laptop. It all comes down to what problem you're trying to solve with your laptop. For me, it was portability. And a tablet gives me more of that than my laptop does.
Until a couple of weeks ago, my laptop was my primary weapon. It had, pretty much, stopped using my desktop, except for big computing chores (or when I needed my two-monitor setup). I also thought that the iPads were pretty pointless when they first came out. However, since then, I've noticed that, many times, I'll be laying in bed at night and I'll want to check my mail really quick, or go look up some website, etc. My two options were: 1) Do it on my iPhone, or 2) Walk across the room to get my heavy laptop and either wait for it to boot or come out of sleep mode, sit up so that I could use it while it was on my lap, etc. So, usually, I'd just do it on my iPhone.
So, I figured I'd get an iPad to see if it would "hit the spot" as far as what I was looking for: an always-handy, quick-on mail-reader, web-browser, media-player. And, as it turns out, it was. Since I bought my iPad, I've gone from only using my laptop to using a combination of my iPad and desktop. The desktop is used for coding, heavy web surfing, and preparing content for the iPad. For everything else, I just take my iPad with me. All of that stuff the columnist gripes that he needs (DVD burner, USB ports, etc), I use the ones on the desktop.
Now, one of the unexpected things about my iPad is that some of the apps (Facebook, Match.com, eBay, eTrade, and Weather Channel immediately come to mind) are actually better than on my PC! At first, I didn't understand how this could be. And then it dawned on my that, on my PC, the interface was always through a web browser. On my iPad, I had a custom app for each of these sites, so the UI was uniquely designed to give me a better user experience. I wasn't expecting that at all. In fact, I actually prefer to use the iPad app for some of these sites over using a PC.
So, all in all, I think the columnist is being a bit unfair (in that he's using limitations of the iPad as an indictment of tablets, in general, and also by not acknowledging that, in all of the ways that laptops beat tablets, desktops beat laptops). But, hey, nobody said that tablets (or laptops, for that matter) were for everybody. So, he's not one of the target market. So what?