My opinion.
I bought many add ons, installed all of them (more than 100), and in the end, developer support is what is the most important thing.
There is some addons that was coded good, and I do not have much problem with them in last few years. Some of them have many bugs, but than it is up to developer behavior, will he try to solve problems or not.
My expirience tell me that this guys are fine coders:
@Xon,
@au lait,
@Bob,
@Chris D,
@SneakyDave,
@Siropu,
@wmtech,
@BassMan,
@AndyB,
@Arty and
@rellect
That is list of coders that I trust because if I report them some bug, at least I have an answer "OK, I will try to reproduce it and I will try to resolve problem".
That is list of developers I trust, and if several coders has same addon, I will choose their. Of course, that in future this list can grow with another coders, but several other coders are on my never buy again list.
Sorry for my language