I've had 21's for a long time; the 3.4 SA has been one of my favourite lenses ever, the Elmarit was doable but not outstanding, but the ASPH is amazing! I got mine shortly after it came out 7 or 8 years ago, and it would be one of the last lenses I gave up. I tested it for the LHSA Viewfinder some years back against the 3.4 SA, the 21/4 Cosina and the 3.5 Ricoh. There was no doubt the ASPH was the class of the field in every respect except size, price and distortion. The SA still had very slightly less distortion.
I have or have had about 20 other lenses close to this focal length over the last 35 years, and nothing else comes close.
As far as shooting scenery, the 21 can be very effective but it does take some practice. I took it trekking in Nepal in 1997 and used it about 10% of the time.
Henning