Upgrade to a K-50 worth it?

I bought a Ist-DS in 2005, and I was quite happy with it.

I bought a K30 in march 2014, and my Ist-DS nows sits in a drawer most of the time.

K30 and K50 are very similar cameras, sharing same sensor, shutter and processor. K50 is a little upgrade from K30, mainly in body design and improving some details (that is what Ricoh claims, I didnt check....).

IMO, K30-K50 have much better IQ than Ist-DS at any setting, delivering much more sharpness and details eve with legacy or old entry level kit lenses, with an improved jpeg engine that can really be tuned to your taste (sharpening, saturation, contrast, hihlight and shadows rendering, WB, aso...).

But IMO the greatest improvements for everyday use are:

1. low-light AF: K30/K50 will AF in dark scenes, even at night, when the Ist-DS AF wont AF.
2. low_light shooting: K30/K50 IQ at ISO 1600 is very good, even for large prints or viewing at pixel level; IQ at ISO 3200 is better than Ist-DS at ISO 1600. ISO 6400 is usable for night shots.
3. stabilization: the IBIS in K30/K50 allows you to shoot at very low shutter speeds for indoors or lowlight scenes: I get a high keeper rate shooting handheld at 1/15 in wide angle and 1/50 in moderate telephoto (up to 100 mm), 1/100 at 135mm. So you dont really need to buy big and expensive f2.8 zoom lenses.
4. you can use recent improved zoom lenses that dont have the screwdrive AF, like the DA 18-135 (WR and very convenient universal range in a compact lens, my favorite for travel), DA 17-70 (very sharp from corner to corner, and convenient range with constant f4), or DA 16-85 (IMO the recent evolution from DA 17-70, which I dont have but seems much praised by users)
5. when shooting jpeg, distorsion, corner falloff and CA can be automatically corrected in-camera (I mainly shoot jpeg or raw+jpeg in difficult lightning conditions; the raw can be corrected in PP through automatic camera profiles in LR or other PP softwares)
6. 16MP pictures allow a good amount of cropping in PP, especially when shooting with sharp primes like DA 21 or DA 70 limited, DA 35 or FA 50.
7. the processor is really faster, which means the camera is almost always ready to shoot, even if you save raw+jpeg.
8. you can display a level gauge in the OVF and/or on the back lcd that tells you if your camera is horizontal (also works in portrait mode), and there is also an option to autocorrect the horizontality up to +- 1 ° (very useful for landscapes).
9. 2 wheels for AE settings is very convenient, whereas Ist-DS had only one
10. Liveview on the back LCD is very convenient in some shooting situations or for manual focus and allows occasional video shooting.
11. WR (as long as you also use a WR lens) allows you not to worry about rain or wind anymore (I got drenched by a tropical rain while hiking in Moorea, French Polynesia: though I had a raincoat, I had to change my underwears once back to my car, but the camera kept shooting and all I had to do was to wipe it)