"This is my third project with this provider. We are working out the development specifications on a fourth project now.
I think the positive attributes are definitely communication and an overall willingness to satisfy the needs of the client. I can only measure skill by the quality of the final product which so far has been very good.
Scope creep is something they seem to deal reasonably well with. There are always unintentional consequences that surface when doing these types of projects. So if you deviate too far off the original dev specs, you can expect a change order.
As for pricing, I'd say he is very competitive. Over the past 20 years on Elance/Upwork, I have paid less and more with other providers, but the true cost of any development can swing based on how many hours you need to spend on validation testing and code changes. His pricing seems fair and reasonable - all things considered.
More important, Joona is building his business and has a genuine desire to turn out good work and make his clients happy. Sometimes that's all you need for a successful project."