This is a very overdue post, since I got my 3DS capture card from Merki a couple of months ago now, but I've been meaning to write some feedback here since I got it.
I sent in my own regular 3DS to Merki and I couldn't be happier with the quality of my capture card and the customer service I received. Merki was really fast at installing my CC and then sending it back to me - very impressed. I ended up getting sick around the time I had hoped to send my 3DS to him, so had to send it a bit late, and Merki emailed me to check it hadn't been lost and let me know he would work on it as soon as it arrived, since he had already reached my order number. 10/10 for service and communication. I've been using my CC for a while now (on Mac) and it works perfectly, no issues at all! Thank you so much!!