I had the opportunity to play with the PDK for half a week. I have to say I found it easy enough to do things quickly. I do have some programming experience that helped the quickness, but it is nice. I spent arround two afternoons playing with the PDK trying to make a silly sinus/cosinus generator, got to know the PDK somewhat superficially… Then I interrupted the easy trigonometric generator, and started to work on a more interesting idea 
That is how I got to making a LEGO Filter. Below, is a screenshot. The basic working concept (without any user control (parameters) took about two hours to code up. Then adding parameters was easy… But some bugs started appearing as divisions by zero and scalling issues came in to play… That took about one day to overcome… Then, the next day, I spent doing some upgrades and adding flexibility. Then, I stoped for about 5 days to take short vacations, and now I am back at it, to perfect it even more… It works fine, though there are some tiny edges I’d like to polish.
Anyway this is what it can do:
So for time consupsion in making a device with the PDK, I think the core part is quick to do if you have your ideas settled. You then take some time in thinking what parameters should the user have access to. You then take even more time solving bugs. And the remaining 90% of the time, you spend in polishing things, as typical of any programming activity 
Oh, regarding debugging, I haven’t really tried debugging in the “normal way” yet, using a debugging environment. I used the “MessaBox” method… Silly and anoying, but it was ok, for something as simple as this filter.
Ok, now for what this filter does: it grabs any heighfield and converts it to a pile of LEGO blocks You can choose the type of stud (flat plate, normal stud, technic stud, or optional heightfield: so you can make your own studs ) You can specify the size of the LEGO blocks, and you can use LEGO plates (1/3 the height) also. You can also choose 1x1 or 2x2 blocks.
It is not 100% finished yet 
I am trying to make things look right in explorer, as the blocks are discreet, they can look a bit disapointing for some parameter values, and I m trying to get the best possible compromises to have something that works and still looks good. Soon I’ll give you the plug-in, but for now, you have to content with the screenshot…
Happy PDK-ing,