and RAM, and hard drives, and graphics cards... I suspect 2014 will be my last high-end desktop purchase.
But that gap is rapidly diminishing - the phones are catching up.
And as for user experience, you need to be able to get a "proper" desktop OS, and you need to not have to plug in lots of cables. And it needs to be able to drive a sufficiently high resolution display at good speed. It's slowly getting there, but it's got a bit to go still (but consider that today, mid-range Chinese unknown brands churn out quad core Android tablets with 2560x1600, and even low end phones come with 1920x1080 screens; and many of these devices can handle 3840x2160 output to external screens...)
Eventually low-power portable-class computing hardware will be as powerful as typical desktop systems today. Though there will likely always be a niche for even higher performance machines.
Price will come down with volume and greater competition as the market matures, as it always does.
And the OSes will get better as people spend more time on these devices and developers spend more time targetting them and working out the appropriate UI optimizations for mobile vs. desktop modes.
Already we have tablets running x86 with good enough battery life, better power than the ARM counterparts, and a full OS, with external hardware support.
Sure, it's not completely there yet, but considering it's $399 today for something that is pretty damned close (and close enough that my girlfriend just ordered one, to use for most of her primary computing, but coupled with the active digitizer for sketching; basically, a netbook), it's only a matter of time before this is completely doable!
Without a large base to spread costs over, it will become a more and more specialised field.
Both Intel & AMD are moving towards not selling individual CPUs and instead having them built into the main board, and I imagine that after that RAM will become built in as well.
GPUs are disappearing from the low end (onboard is getting pretty good) and if Intel succeed with Xeon Phi cards, thats going to start splitting the HPC market away from GPUs. Without the low end to get rid of older stock and increase the yield, I could very well come that Nvidia and AMD aren't able to keep the R&D dollars in GPUs.
Component manufacturers will start exclusively targeting consumer electronic companies, and the Off the shelf market may find that it is forced to pay premium prices, further reducing the number of people who are participating.
Unfortunately consolidation is a sign of a maturing market, with most people being happy with an off the shelf system (i.e. most people even on HN are happy with a macbook pro / air and its limited upgradability). A quad core laptop, 8gb of ram and 256gb SSD is suitable for most people, especially if they have a way of storing another 1tb of rarely used content (external hdd, NAS, online storage). They have been available for the past 3 years, and we are starting to get to the stage where they will likely be suitable for the next 3 as well. It will be a shame as the days of building cheap consumer grade servers for home use will be behind us, as will High performance workstations for 1/3rd of cost of Dell / HP / whoever.
For me it was 2002. Since then I have only bought laptops.