Olle, do you sell these kits? Appears you are well thought of.
No, I don't sell any kits, I'm just such a nice guy.

Seriously, I have done a few brake conversions, and have usually used junk yard part. For my latest project though, I decided to look into the kits and did some pretty thorough research. Some of the things I found out about the basic OEM-style kits were:
-Many of them (if not all) use the same spindles. I guess the market doesn't allow for too many manufacturers
-Many of them use generic, ugly looking boosters
-Most of them don't include brake lines, vacuum line and fittings but they can be ordered separately
-Most of them are pretty much identical, but the price can still vary $150-200 or so.
-Many of them use cheap, Chinese made hardware (bearings, seals and such)
The vendor I finally picked had a very reasonably priced kit, with a nice restoration grade booster (no Delco stamps though), answered all my e-mail promptly and delivered quickly. You'll get an idea of what to anticipate if you check the review I wrote, but in short: I'm sure that I didn't have any problems that you wouldn't have with any other kit. I haven't seen the seller on eBay lately, but you could send him an e-mail and see what he says.
Best of all: I already had some old part that I wanted to use, and I didn't have to buy a complete kit. He was more than happy to sell just the parts I needed.