It's not the money, that's for sure. Here is my view on the E3D, which will probably not be very popular.
I've personally never had any (major) problems with the original hot end, and since I only print ABS and have no interest in printing with other materials (at the moment), I see no reason to change.
I personally don't believe it can improve your printing quality. I know many people swear by it, but to me this is more of a placebo effect. Most of those that went with an E3D, did so because the hype around it, and because they were having so many printing problems they believed that this would be the end all, be all, that will magically make their printer work.
It's not. In fact for most beginners that (the hot end) is NOT the first thing they should change, there are many other things wrong with the printer that need changing, but the print head is not one of them.
Additionally, most of those that did do the upgrade, also changed other things at the same time (like the extruder & carriage), that they have no idea what it was that made their printer work better than before, but they think it was the hot end, because they believe in the hype.
Contrary to the popular belief HERE, the MG Plus hot end is well regarded in the RepRap community as a good workhorse. The quality of the heater block, and the way Soliddodle chose to attach the thermistor are questionable, but the MG design is solid. I've always had good quality prints and the problems I'm currently experiencing are due to other factors (vref or hysteresis issues for my banding, or crap filament for clogging).
In my point of view, the E3D, and other similar all-metal hot ends, are a good upgrade for the advanced users that want to print exotic materials such as nylon, metallic or similar materials that require hotter temps. Most users though, will settle for ABS or PLA, and they really have no need for a E3D/all metal hot end, which introduces its own issues that these very same users are not really prepared to deal with like flashing firmware, re-adjusting the print bed height, Printing a new Extruder, which inevitably leads to printing new carriage for it, which leads to the replacement of the rods, since the stock don't work well with linear bearings, etc, etc.
In fact, for most users I would recommend a "fix" to existing hot end, but only if they're having extrusion problems. Get a new heater block and a cartridge heater. About $6-7 worth of parts, and replace the aluminum heater block and the heater resistor with these new parts, leaving the rest intact. 10 minute fix, no firmware, not new extruder parts, no new calibrations, just plug and play.
To print or, 3D print, that is the question...
SD3 printer w/too many mods, Printrbot Simple Maker Ed., FormLabs Form 1+
AnyCubic Photon, Shining 3D EinScan-S & Atlas 3D scanners...
...and too much time on my hands.
