I am very happy with this app 99% of the time, and the other 1% of the time it drives me nuts !
I should start by saying that when I signed up, it was the only app I could find which would take products from Shopify into E-Bay, and then take the orders from E-Bay back into Shopify, and do all that at the price which a small business could tolerate. So thumbs up on that.
The set-up process was quite onerous, not because Inkfrog is difficult or obtuse, but because there is a 'best practice' way to operate Inkfrog to give yourself the minimum of problems. If you follow that method, then life begins to settle down, if not, stand by for a bumpy ride.
I strongly recommend taking advantage of the offer of a call with an Inkfrog support representative before you get too deep into the software. I did this perhaps a little bit later than I should of, and did it because I kept having problems with products not syncing properly, wrong photo's being uploaded, prices being changed etc. I had to do something about these problems because as anyone selling on E-Bay knows, you are on a very short leash.
I follow the Inkfrog best practice to the letter now, and the problems are very much reduced. There is still the occasional blip, however whether the issue is within Inkfrog, or because E-Bay or Shopify have changed something, is generally impossible to tell.
I have found the Inkfrog support team to respond very quickly on the whole, I have never been left without a solution, and generally the solution is there within a couple of hours. However, what I have rarely been able to find out, is why the problem occurred in the first place. This is really important to know in my view, because if the problem is my own process, I want to know about it so I can prevent further issues.
Aside from the occasional unexplained glitch, my main gripes about the software would be that in order to avoid sync problems, every time a new product or products is created in Shopify, Inkfrog will not pick that up unless the product download file is rebuilt from scratch. This is an automated process, but if you have products into the thousands, this can take a while to do.
The other main issue is that for existing products on Shopify, if you amend the photo's, these are not automatically updated in E-Bay. I believe the Inkfrog team are working on that feature though.
So, in my view, for the money, there is no better app that will do all that it does, but be prepared to put a lot of work in to getting it working for you properly. I would also say that I am not 100% comfortable that I can 'ignore' Inkfrog and let it work in the background, errors do still occur, and you would be wise to log in and check for anomalies on a daily basis.