Been using a 13-inch i5 retina from late 2012 on the daily and it's held up fairly well.
8GB of RAM with a 256GB SSD that's still in fairly good health that doesn't leave me wanting for much more, even with the occasional heavy usage. Definitely not enough RAM for a decently-resourced VM or HD space to adequately work with dual booting, but that's just been my experience in software development and flirting with a few pre-2011 games under Windows with the graphics settings turned way down.
Safari's ... kind of a struggle with a known page rendering issue if you two finger swipe with the touchpad to go back instead of using the back button, but it provides the best battery life and respectable performance. I still mainly use it even in spite of Apple's misguided attempts to drive everyone out of its ecosystem with the death and near end-of-life for many extensions I enjoy.
Firefox has some issues that can leave your laptop overheating and the browser's performance too sluggish to bother using.
Chrome's been a champ performance-wise, but it drains battery even when in the background, as expected.
Since it's a dual-core, hyperthreaded system, it's pretty much a 2.9GHz part (base 2.5/dual boost 2.9/single boost 3.1), though I've never once seen it boost a single thread to its maximum rated 3.1GHz speed -- and I keep a close eye on these types of things as a sort of curiosity.
The integrated HD4000 graphics is really showing its age with the transparency effects in Mojave that I'd love to disable, but the sound and brightness overlays are so huge as to look off-putting when opaque so I just put up with it. If you don't mind it, you can disable them in System Preferences > Accessibility and spare your lap some of the heat generated when the graphics rev up from 800MHz to 1.1GHz just to overlay some transparency effect.
Since it's a Retina display, its defaulted to a 1280x800 resolution, which, while it does look crisp, is thoroughly useless for any sort of multi-tasking. I leave it on a scaled 1440x900 which has such a negligible effect on performance that you will never notice it. 1680x1050 is also available at the high-end for scaling with a similarly unnoticeable effect on performance (you'll notice the slightest delay when activating Mission Control), but everything is rendered too tiny for me to use this mode for any period of time.
With light usage, it stays fairly cool (41C - 60C), but can hit as high as 94C with the HD4000 integrated graphics fully engaged.
Power draw ranges from a light 8w-13w, a moderate 16w-20w, and a heavy 35w-40w with screen brightness, Turbo Boost and Graphics going. This leads to a battery life that can go from 5:30 to 6 hours light usage, 4 hours video playback and 2:30 to 3 heavy usage after a battery replacement + kit from ifixit.
I love the keyboard on this thing. It has that chiclet, island-style layout but with adequate travel and spring. Keys feel firm and have a nice clickiness to them. Never had a single problem with any of them, even when I use a non-static spudger to scrape them clean. The backlit keyboard is even and shines through the letters of the keys and around the edges so you can see them perfectly at night. I honestly avoided upgrading due to the issues and feedback on the newer-style butterfly switch. It's really too good to give up.
Trackpad is huge and still physically clicks, if you're not into that force feedback stuff that Apple switched to. It feels fine on my iPhone 8, but I'd rather keep the actual clicking on my laptop.
I fully expect to get a few more years of usage, but don't really expect to see another major MacOS release for it, seeing as how it's pushing 7 years old in October of this year. The integrated graphics generation of Ivy Bridge processors is still really underwhelming and draws the majority of heat-generating power, but the performance of the RAM, SSD and processor are still really good.
For light and medium usage it will keep up with you no problem, but you'll feel the age if you try to push it to anything beyond that. It's still from an era of 22nm, 35W TDP processors going up against today's nearly halved TDP with improved performance.