As a professional wedding photographer, I need a reliable print shop where I can order prints of varying sizes but also have the option available to do some minor touch ups if needed via a workstation. Pikto offers that.
I have placed many orders through these guys and they do a pretty good job each time. The print shop staff are actually pretty nice to work with. They take the time to answer my questions (as long as they're not too swamped with orders) and take care with my prints.
I've also printed a photo book with them. It was okay. Just okay. Think high school yearbook-style of album with fancier cover options. It was a one time deal and I now outsource all of my albums to a company in the US.
The reason why I don't give them a 4 star rating or higher is because of their prices. It's one price for all. Regular Joe or Pro Photog, there's no deviation of pricing (unless you order prints in mass quantities... but that's available for everyone too).
I'd go back more regularly if they offered pro pricing but it doesn't make sense to print with a lab that any of my clients could go to and get their prints for the exact same price. Pricing fail.