Having used a number of those inexpensive Ebay switchers (w/out the metering) - some of which look exactly like the ones in the picture - I can say that they are certainly worth the price, which is less than that for which I can get the parts!
I did build one of these into a device that runs 24H/7D and noting that various parts of these ran "very warm" I:
- Paralleled high-quality, low-ESR capacitors (470uF) on the input and output sides to take some of the stress off the unknown (!) quality capacitors on these boards. (I used Panasonic caps, IIRC).
- Soldered a reasonably large piece of copper bent to an "L" shape to the tab of the IC (such as it is!) to improve heat-sinking.
- Using "JB-Weld" - a metal-filled epoxy capable of reasonably high temperatures, I attached a piece of aluminum bent to a "U" shape to the top of the inductor to get rid of some of its heat which was being transferred to its adjacent components.
Just adding the additional capacitors made a disproportional improvement in the reduction of the switching energy (like that on the pics from the CRO) on the input/output leads - more than you'd expect from the increase in capacitance - implying that the onboard units are probably a bit higher impedance than the new, outboard units. This may have meant that they would be dissipating a bit of heat on their own, probably resulting in reduced lifetime. For as cheap as they are, I wasn't counting on them having very good capacitors (or enough capacitance!) anyway!
My non-contact IR thermometer showed an approximate 10C drop in device temperature after adding the additional heat sinks. This cheap converter has been running 24/7 for about 2 years near its maximum ratings, so that's something!