I have an Ultimak/Aimpoint combo on my Poly Legend and I am very fond of the setup.
The good news:
1: Forget the stuff about the sight getting too hot from sitting on the gas tube. I will tell you as a hard, experimental fact that just carrying the rifle around in the Arizona sunshine will get the scope a lot hotter than shooting the living crap out of the rifle will.
2: The optical quality of both the lens and the electronic reticle of the Aimpoint is vastly better than the Kobra (which I have on my AK74).
3: The Ultimak places the scope a lot further forward than does the Kobra. Anyone who shoots unmagnified electronic scopes will tell you that more eye relief (within the bounds of sanity) is better than less.
4: The Ultimak indexes on the barrel itself and pretty much guarantees that the scope will be parallel to the bore. With the Kobra, you have to worry that A: The left side of the reciever is perfectly parallel to the bore (good luck). B: The scope rail was riveted perfectly to the side of the receiver. C: The process of tightening the scope mount to the reciever allows the mount to remain perfectly parallel to the reciever (real good luck). and D: The whole scope mount apparatus is originally constructed, and will remain through hard usage, in such a way that the scope remains perfectly parallel to the mounting rail (extremely good luck to you). My own ORF/Bulgy 74; a very well made example, will, with the Kobra zero'd perfectly for windage @ 25 yards, shoot 4" to the left @ 100 yards. I don't have that problem with the Ultimak on my 47. Zero windage @ 25 yards equals zero windage @ 200 yards. This is no knock on the Kobra nor on AK's in general. It is simply recognizing the design limitations of side-mounted scopes. M-1's and M-14's (hang on while I put on my Nomex coveralls for the incoming flames) suffer from the same design limitaions. Talk to any one who shoots a scoped M-14 seriously (like John Miller or Derek Martin) and they will tell you that the gun is a ring-tailed mo@#$%^&er to keep accurate.
5: With the Ultimak you can use your normal cheekweld and can even see the iron sights through the scope if the scope dies. With the much higher Kobra, you have to develop something more like a chinweld.
The bad news:
1: The Ultimak/Aimpoint combo will set you back about 270% the cost of a Kobra.
2: Because of the gas system, Ak's are pretty nose-heavy to begin with. The Ultimak makes it more so.