I am certainly a fan of 40 degrees of flap on a Cessna 150, particularly when combined with a Horton STOL kit. Yes, one can easily land in a place too small to take off from!
I agree that the Later Cessna flap preselect switch of the later 150's and 152's is pleasing to use, but they can be more demanding of maintenance though. When they go wrong, they go way wrong!
The original flap switch is the subject of a service bulletin, which suggests its replacement with a spring to center from both position type. This is not mandatory though, and I have preferred to leave mine original. You just have to pay attention a little.
The flap position indicator on the door post is not perfect, but it is an improvement over the earlier version, which was right above the pilot's head (good for instructors to see though). I have devised a very presentable decal which is applied to the inside of the left wing rib aft area, which becomes exposed when the flap is extended. This simply makes 10 degree increment lines become visible as the flap extends. I have not evaluated it on 30 degree flap Cessnas, but I can't see why it would not work. When you're flying left hand circuits, you spend some time looking right out in that direction anyway, so a quick glance, and your flap setting is confirmed. Should anyone wish a CorelDraw file of this decal, PM me and I'll be pleased to sent it along via email. It's installation would not require modification approval by Canadian standards.
I am not of the opinion that flap asymmetry in a single Cessna is a risk of any concern. If it were to happen during extension from flaps up, retracting the flaps would fix the problem. If one flap suddenly retracted from full flaps - forget it, you'd be done, unless you had lot's of altitude, and manual flaps.
A greater risk, and is has happened to me in a Cessna 180 floatplane, is a flap track breaking off. During water touch and go's (way further from shore than I should have been) I quickly retracted from 40 to 20 while on the step, and took off again. The flap handle felt a little funny. Once airborne, I could not move the right flap at all, and the left had become a very unsafe aileron. I flew home with 20 flap out, and landed with that setting, and great care. Once on the water, the right flap hung down inboard at an odd angle. It's track had come completely out of the wing!
One other 152 note; as factory configured, they had a very poor short/soft field takeoff compared to a 150. A different propeller played a part in this. Lots of grass runways I'd been into in a 150 terrified me in a 152.
In 1977, the introduction of the 152 was very anticipated. By chance I was the first person to first solo the first one into Canada. It had 33 hrs TTSN at that time, and my instructor was nearly fired for sending me off in it! Once we got to know them, many of us were every bit as happy back in 150's.
Sparrowhawk is a very worthwhile conversion to a 152.
Pilot DAR