I've used UserTesting (and its service Peek), as well as other user behavior analysis tools like HotJar, Crazy Egg, etc.

To answer your questions:

1. Do you use such services? If so, what do you choose?
// I use them to either confirm or reject hypotheses I have about my product's/business' performance metrics, and gain ideas as to how I could improve them. Best example: my team's goal was to increase the %age of users successfully making it through our onboarding process. We collected a handful of videos via UserTesting, and gained dozens of insights into ways we could simplify and clarify the process - and it resulted in a significant jump in our conversion rate.

2. How you choose it?
// Being in the web/UX design industry for a while, I'd heard of them before (via following relevant Twitter hashtags and UX blogs), and mentally bookmarked them until we had a need. Did a quick price comparison first with other similar services, then decided to pull the trigger. My primary decision criteria were: 1. How much is it? 2. How quickly can we get back data/results, and 3. Are we able to find good-quality, targeted participants that are similar to the kinds of users we're going after?

3. What was the main problem of using such services?
// I don't think we were able to find exactly the types of participants we needed, but we had pretty specific criteria our first time around. Once we relaxed our requirements a bit, things were smooth from that point onwards. This was probably a couple years ago, though, so I would imagine their pool of participants has expanded significantly in breadth, diversity and available targeting criteria since then.

4. If you didn't use it, tell me please why?
5. Will you use such services in future?
// Yep, absolutely. It's one thing to look at the analytics to try and figure out why people aren't doing what you want them to do in your app/on your site; it's a whole other thing to *actually see* what individual users are doing, and hear their rationale in real-time.

I hope that helps - feel free to gimme a call if you have any other questions! ~Jason

This is dependent on the product that you're working on.

We chose not to use any of these services for our own company (meal delivery service) when we operated. We made the decision because we valued the meaningful 1:1 conversations where:

- We knew who the person was
- We controlled the conversation/environment
- We could ask direct follow up questions

And more importantly, it was a true organic conversation. Finding and talking to users is an intimidating process (even more scary than say, building the product and all the technical workload behind that) - but it is a necessity for success in early-stage companies.

Talking to someone naturally and organically can bring about many tangents/threads/anecdotes that you can then pursue to figure out things like:

- Deeper underlying pain points
- Opportunities to build features for
- Production direction that you perhaps didn't consider before
- Validation of past theories about users
- Contradiction to previous theories

All these are hugely important.

In the beginning stages of user-testing and seeing what people think of your product, you absolutely should care about quality over quantity.

1. Do you use such services? If so, what do you choose?

I used UserTesting in the past.

2. How you choose it?

I used it to test new feature ideas and to refine existing UX.

3. What was the main problem of using such services?

It got kind of expensive for us (we were a startup) and sometimes the users were not as targeted as we wanted (especially when we were testing b2b stuff).

4. If you didn't use it, tell me please why?

5. Will you use such services in future?

I now work at a large company so probably not since we have researchers on the team who do their own recruiting and testing. That said, I find the insights from DIY things like userTesting to be good enough especially if you've done testing before and have some experience with user studies and UX design or product management.