I have experimented with several optic-setups on my Romanian AK and this is what I have found:
Two Romanian AK's with Russian optics on siderails. The top is my bro's before he put the Ultimak on it, wearing my PK-AS-V. The bottom is mine with the Kobra EKP-1S-03M mounted.
I initially put a PK-AS-V on the siderail. This is a tubular red dot sight with a circle dot reticle. They appear black like a normal scope when not illuminated. When illuminated, the center dot glows red. The center dot is about 2 MOA, the outside ring was around 50-something MOA, IIRC. It is very fast while still allowing decent precision. It seemed fairly durable as well. Now the cons; the optic sits too high to allow a proper cheek weld with pretty much any stock setup. The PK-AS has external adjustments, and requires the optic be removed from the rifle to access one of the adjustment knobs. The adjustment knobs are only marked in Russian and they lack the tactile clicks of Western optics. This makes it much more difficult than Western optics to properly zero. Finally, it doesn't have the battery life of some American optics and once mine went dead, I have been unable to get the sight to work. I have bought several of the '357' style batteries the manual said would work, and they don't. The reticle is still visible without being illuminated, but as of now, mine is a dot sight, not a red dot sight.
I'd give it a 2.5 out of 5 stars overall.
View through PK-AS across ~12 foot bedroom.
I replaced this optic with a Kobra EKP-1S-03M, which is the newer AA battery model. This model sits lower than the PK-AS-V, allowing for a better cheek weld. It has multiple reticles, though I've just put mine on the chevron and left it pretty much since I got it. Replacement batteries actually work for this optic, and as it requires common AA batteries, they are easy to find. It also has internal adjustments, which makes it easier to zero, though you will still have to read Russian. I've taken mine out in the snow to play a little, but have no experience with the rain/washout issue.
Mine has been pretty solid and I definitely rate this set up higher than the PK-AS-V--call it a 3.5 out of 5 stars.
View of 16" wide torso target at 50 yards through Kobra with chevron reticle.
Overall, the siderail mount has been fast and repeatable for me. It is a decent setup, and as the Russian siderail optics are of decent quality, they represent a great value. Most of them can be had for ~$200. I have yet to see an American optic with similar features and quality at the same price. However, one thing that bears consideration is that if your receiver isn't square, it can bring the rail far enough out of alignment that is it difficult to zero the optic. As my WASR was assembled by Century's barely literate poorly trained monkeys, I have encountered this problem. The PK-AS was simply a PITA to zero. The Kobra would have been simple, but I ran out of windage adjustment trying to get it on @ 100 yards. The rifle groups respectably for a rifle of its type--about 4 MOA, but I can't adjust it the 2 to 3 MOA to the right that I need to in order to get it properly zeroed. While this isn't an issue at across the street distances, it quickly becomes an issue as you reach 100+ yards.
This leaves me with forward mounted optics options. I ordered an Irondot, but it was so backordered I canceled my order. My brother has an Ultimak with an Aimpoint CCO on it. This is really a great setup. It is low enough to co-witness, something none of the siderail mounted setups can claim. It is rugged and repeatable. However, it heats up. The Aimpoints can take the heat, some of the others, not so much. The Aimpoint, is an excellent candidate for the Ultimak for its durability as well as its battery life, which is exceptional. The 2 MOA dot is fast while providing enough precision to reach out to 200+ yards. It zeroes easy and the Ultimak keeps its zero. Unfortunately, this set up costs nearly 3x as much as the siderail setups. I feel it is worth it, and if I ever get around to replacing the Kobra on my AK, it will be an Ultimak/Aimpoint T1 setup. Of the setups I've seen, it is by far the best thing going for the AK.