Pros
Purr Group is a fantastic place to work. I worked for the company for a number of years and achieved a lot, both personally and professionally. I had to leave because I needed to move to another city, but if circumstances were different I have no doubt that I would still be a happy member of the team at Purr.
They manage to strike a great balance between all things that are important to a company and workplace. This goes from a great team atmosphere and a comfortable office to excellent projects and plenty of room for career development. There really is nothing that's lacking. If you happen to interview for Purr, or are potentially going to be working with/for them in another way then trust the positive feeling you get from the place and the people - you're not wrong.
Cons
Not much I can say here. I suppose that Purr is still a relatively small company, there's no getting away from that. So this means there may be some things that are important to you that are only available at big companies. Like if you wanted to travel a lot with work or something like that, or work in a team of 20+ developers, it's unlikely that you'll be able to do that with Purr as readily as you could with a bigger company. Personally, this was never an issue for me, as I wanted that small-company mentality, even if it meant sacrificing some of the big-company perks. I don't want to speak on behalf of my former colleagues, but I'd imagine they would say the same too.