The Leica MP incorporates many features reminiscent of the M3 , whilst including some modern advancements such as a built in exposure meter. Also, the construction is more on-par with the M3 , M2 and M4 , maintaining a higher standard compared to today's leica M7 , M6 , M9 etc. The top panel and bottom baseplate are both machined from solid brass, unlike the magnesium ones of the M6 . Also, unlike the M7 , as the word-of-mouth name sugggests, the Leica MP is fully mechanical, i.e. it can operate fully without any batteries. This is not to say that it does not have a lightmeter; it does. The light meter shows in the viewfinder to indicate whether the exposure is due to be under, over, or correctly exposed. There are two triangles either side of a centered dot to indicate whether to increase or reduce exposure time.
Another feature, taken directly from the Leica M3, M2 and M4 is the fully metal, machined film-advance lever. Unlike the M6 and M7 advance levers with the plastic converings, the MP's advance lever is a solid piece of metal, in the same shape of the M3's. Also, the film-rewind knob is now a knob rather than a crank or lever. This too is identical to the one on the M3. The change from the angled cran on the M7 to the straight rewind knob on the MP is due to problems users sometimes encountered when rewinding their film; the film would sometimes jam, and the components were more likely to give way due to the complex mechanics of the angled rewind knob. Thus, the MP is somehwat more mechanically perfect than its M7 sister/brother/partner...
A minor 'upgrade' so to speak over the revered M3 is native support for the Lecavit winder, which helps achieve faster film advance. The M3 had to be modified in order to accept the Leicavit winder and function.
Another minor but needed upgrade was the viewfinder. The finder on the M6 and M7 was very prone to flaring, and many times when in a source of bright light the rangefinder patch would partially or completely dissapera, disabling the camera's focusing mechanism and capabilities. The MP has the addition a new element in the finder, which eliminates this problem, and this upgrade is available to owners of the M6 and M7.
Lastly, it is said that the shutter button and film-advance lever is more similar to the one on the M3, both in feel and action. Once the MP is broken in, users claim that releasing the shutter and advancing the film is the same religeous experience that it is on the M3.
The Leica MP can be seen as the reincarnation of the legnedary M3. The mechanics are simlar, offering a bare-bones rangefinder photographic experience. The addition of a built in light meter adds modern-day convenience without taking from the all mechanical experience. The construction and elements used greatly resemble the original M3, essentially making the Leica MP the quintesesntial classically modern rangefinder camera.