If you do purely digital stuff, there is not much to measure that need _accurate_ info about R, L or C. E.g. supply caps might need to be checked, but a crude value from a DMM is enough for that. Very high speed digital might need some impedance checks, though, but the impedances are usually "by design" (PCB trace geometries), and whether such trace works properly or not can be seen with oscilloscope (which is in general more useful in digital stuff than LCR-meter).
So far the nearest to digital measurement that I have done (and with DE-5000, too) was to measure a detached SMD cap part of the 5V standby supply circuit of a PC PSU. Just to see if it was still ok (within a range of values that made sense according to the datasheet). Accuracy was only semi-critical, but most DMMs don't do SMD caps conveniently, especially very low value ones. Also, a blown SMD resistor in the same PSU, which was of so low value that my DMM doesn't measure there (with sensible accuracy). To my surprise, that blown resistor was still ok, but I replaced it anyway.
As soon as you start connecting to analog stuff, the DE-5000 might come handy. Say, controlling motors (fans, steppers, anything), speakers, current measurement (with sense resistor(s)), some power supply types, etc.
Whether its accuracy is enough for "research and development" depends solely on what is needed in a particular task.