I've used it and am happy with it. It's reasonably reliable, but has more downtime than the big providers. I wouldn't run mission-critical software that needs 5 9's uptime on it, but for anything else it's fine, certainly for personal projects. They're transparent with any outages, so you can check up on the outage history on their blog:
https://prgmr.com/blog/It's a small business run by a few people (though it's been around for 10 years, so a pretty stable one), which has the pros and cons that go along with that. The tech staff is good, techies who know what they're doing and generally assume that you do also. So if you send a request or problem report, you aren't going to get a form reply that asks if you tried turning it off and back on again. But it's just a handful of people, so if there's a major issue, fixing things is pretty manual and slower than at places that have armies of 24/7 devops staff.
One specific thing I really like about it: it gives you SSH access to a proper text console, in case you want to install a custom OS, recover a broken install, etc. Most VPS providers give you console access, but most do it via VNC in the browser, which is not my favorite way to do sysadmin work.