mb,
You know manufacturers are supposed to provide every new product buyers can think of the day after the part is requested with all R&D conducted within that 24hr window and priced below mfg costs to include overnight shipping. The part must work 100% of the time for the entire life of the buyer no matter how he/she takes care of or handles the product.
And as soon as you make a part no one else in the world is making, buyers will complain you didn't make it do "this" or "that" or it should have looked different, or they wouldn't have done it that way, etc., etc.
Don't forget that if a customer complains about your product, you must send a check or the purchase price and a new part within 24hr to include shipping. Oh, they will send the bad part back to after they have tested the new part or keep for their troubles.
You must also wait by the computer/phone/fax machine 24hrs a day in case a buyer has an issue with your product.
Don't you just love "Great Idea Fairies"?

Humm... where to start...
The best thing I can say is at least I like R&D. Mostly.

I have been very lucky with a great client base to date. From customers and others I get a ton of ideas - some aren't as workable as others - but none the less, it's been very positive. This whole process for me has been a learning curve. Sure, sometimes you get someone who's looking for a reason to gripe or whatever and two of those guys are still trying to order one of my standard lowers.
Other people are positive experiences. Some now have that prize piece and are content, a lot become repeat customers and a few offer up ideas that they would either like to see become a reality or have a product idea of their own. I try to give everybody a little time, from idea pitches to inquiries about what if any, work I have available.
But Tango, I see and have experienced what you're talking about and have been lucky so far. Sure I've felt a little of that pain (think pistol caliber lowers...), but overall, something must be ok because I keep doing this. My other business... well, that's another story. And maybe a glass of bourbon.
For the casual reader of this, R&D for me takes a long time and drives my wife crazy. Some pieces and parts have been floating around forever and will never make beyond being on paper. Others end up part way and never progress. Anyone want to buy a billet lower cut for a Thompson mag or how about one for a Sten mag that's cut .300" further back??
Give me a solution to a problem that I can pound out in 24 hours and I will find a reason it will fail before 24 hours is up. I've got a tub of scrap to prove it. Well, that and some credit card bills!