I've bought several things from Tindie. Generally, the items have arrived, and I have had few issues with quality (though with some of the things I bought, I wasn't expecting a slick finished product, but that is fine, not everything needs to be slick).
Until about 6 months ago, it seemed to be populated with mostly maker made stuff. I.e. somebody designs an add-on board, or trinket and sells a few items. In that sense, I think it was successful in that it would allow people to find more unique items. It sort of reminded me of where people might go after an initial kickstarter project (back before KS itself became too big) that was mildly successful, but not enough to found a company with. I.e. a place to buy/sell hobby boards.
However, I suspect it wasn't as successful in terms of revenue for the owner. Somewhere around 6 months ago, things changed. Suddenly, there were more big players, and not everybody seemed to be making their own products. Two companies seemed to show case this for me. One is bbtech (black box tech) is a Chinese manufacturing company, and most of their products look like knock offs of other products. Now, the products generally do look well designed from the photos (and the protoboards I bought which seem to be knock offs of the Adafruit perma-proto boards), but I felt it changed the focus of makers selling speciality items, to just a place the big vendors can sell their stuff. I am reminded of the scene in Butch Cassidy and the Sundance Kid where the sheriff gathers the crowd, and the salesman then starts trying to hawk his snake oil to the crowd assembled.
The other telltale sign of change was when Schmartboard started selling there. Schmartboard sells and designs prototype boards, and sells them all over (at Radio Shack, Amazon, and their own store). Again, it felt like the small guys were being pushed out.
I complained about these two things in the forums (that had very little traffic), and the owner came off to me as sort of glib, and saying they would monitor things, but I didn't notice any change.
In the last month, things have changed even more. There are now many more categories. The problem is with many more categories, it makes it hard to find unique things that you didn't know existed without following every group (which to me was the appeal of tindie). Also, you have the general problem of picking categories, etc.
Previously, they had a place where you could ask questions of the seller, and the answers would be public, including answers if any (and one of my dings against bbtech was I asked a question about their board, and it never got answered). Now, questions/answers are done via private mail, and you can't see all of the questions asked previously. As I mentioned there was a forum area, and now it seems to be missing.
There are several Teensy related products on tindie.
- TallDog's Teensy breakout board: https://www.tindie.com/products/loglow/teensy-31-breakout/. I bought the previous 2 versions of the board, and I'm just getting confident in my soldering skills to attempt soldering the pins for connecting the bottom pins on the Teensy, but I haven't actually used it yet. The current board is a tweak of one of the previous two designs (the other design has been retired). I don't recall if TallDog ever post about the breakout board on this forum.
- Pico's Teensy 3.x Arduino shield + nRF2401+ header: https://www.tindie.com/products/pico/rfx-teensy-3x-nrf24l01-carrier-board-w-prototyping-area-/. I haven't bought this yet, but I may in the future, as I have bought some nRF2401+'s, and want to play with them. Pico announced this shield on the forum.
- Petit Studio's Teensy 3.x Arduino shield with access to the bottom pins: https://www.tindie.com/products/freto/teensy-3-breakout-board-and-shield/. I believe the author of this shield posts as freto here. I bought one (fully assembled), and it came out really nice. I had some minor niggles about the design (but then I have minor niggles about every design).
- Pesky Products recently posted two LSM9DS0 Teensy 3.x shields, a mini-shield https://www.tindie.com/products/onehorse/lsm9ds0-teensy-31-mini-shield/, and a mini add-on shield: https://www.tindie.com/products/onehorse/mpu9250-mini-add-on-shield-for-teensy-31/
- There are a few Teensy 2.0 shields (Apple connectors, signal routing matrix, etc.) that I haven't paid attention to.
So I used to be very happy with tindie. I am less happy now, but I still scan the site once a day for new shiny's.