I'm an early adopter and first of all:
I still see this as a good investment, because i'm thinking in a long term.

SyncSpider was one of the earlier "Zapier-like tools", but it's not exactly like Zapier - that's good to know before you buy. And it's even less like the other tools that came later, like Integrately or Pabbly, just to name a few. I use them as well, but for other things.

What's the main difference for me? SyncSpider offers a very solid API-connection. That has got nothing to do with the webhook-based tools above. One main difference: You can do things like a "full load". Like that you can change your CRM and transfer your shop-data to the new one in a very short time. That's a big Plus for me.

Are there downsides? Yes, API-development takes more time. That's what they announced from the beginning and it came true, beside the hype that was made by others. So you need patience - that's why i said, for me it's a long-term investment and it totally depends on the apps you need. So there's no point in comparing it with the other webhook-based players (that's comparing apples with oranges). It took some time to get the integrations i need, and some aren't here till now. But they will come, i know :)

A good point for me is their support. They are not always the fastest, but they are really trying to solve your problem! I had a few specific needs and i lots of them were solved. Also, the support is very friendly, nice guys like you and me. At least as me

Another important thing for me is GDPR! They live in Europe, have servers in Europe and they know what i'm concerned about. How many times i've read in the LTD-space "We are GDPR-ready" - this time it's really, really true :) This might not be important for everyone, but for me this is essential and means less headaches.

So, buy this if you want a solid solution with some extras. If you need a fast solution, take a look at their existing integrations first and see, if the apps you need are already integrated.