Yes, it's currently doing what it should because I sized it correctly at the last upgrade (4 years ago), but its current memory usage tells me it's near EOL for me - and I wasn't particularly busy yesterday (only 2 VMs running). I've been in the computer business for over 40 years - I know how to do capacity planning. As I said, I can probably squeak by for a year before an upgrade is mandatory.
Apple won't *let* me size a machine correctly for an upgrade this cycle. Remember, it has to last 4 years. Dell, on the other hand, will sell me a machine with twice the memory in a very similar form factor (1TB PCIe SSD, same processor, same weight, about 1mm thicker, but not as wide) for about 700 dollars less. It will also have a bloody ESC key. It won't have a MagSafe, but then neither will the MBP. Yes it will come with infected with Windows, but it will take me about 20 minutes to eliminate that particular problem (I've been running Linux since the 0.92 kernel back in the mid-90s). I'll miss the tight integration with my iPhone and I'll have to cobble together something equivalent to the multilevel Time Machine-based NAS backup scheme we have running here at the house (we have 5 Macs here), but then I do this stuff for a living so it's not particularly difficult, just time-consuming.
It is possible (but in my experience wildly improbable) that a Dell will be less reliable than the MBP. My rMBP was out of commission for various hardware issues 4 times while it was still under AppleCare (and twice after that - the most recent occurrence took an email to Tim Cook to resolve). I think it is unlikely that a botched attempt by Dell to replace a faulty trackpad will result in the wholesale replacement of essentially the entire laptop (except the outer case and the SSD) - which is what happened to the rMBP 2 months after purchase (the rMBP is so hard to repair even Apple can't do it without breaking something critical half the time). I'm on my third motherboard in this thing. I blame myself - I was an early adopter and Apple frequently has initial quality control issues with new hardware.
By the way - I do agree with you that it's "all about compromises" - in this case, it's about compromising functionality to conform to an esthetic and marketing vision that has pretty much nothing to do with the usefulness of the machine as a tool (which is all it is for me). Yes, "pretty is a feature" (a notion that, by the way, originated with Seymour Cray on the CDC 7600, not with Steve Jobs) but it shouldn't be the only feature.
