The data from sites like ours, is identical in terms of its format to amateur data and does not require doing anything different — other than we handle all of the preprocessing tasks ahead of time and customers engage with master data only.
I recently started using Dark Matters - the data is high quality: long exposures (30+ hours in my datasets), nice targets, and excellent service.
TL was great, but they changed with the release of TL4. I'm using my remaining credits with them and likely won't continue (however, they are publishing nice solar images, so I might keep their most basic membership ($6/month) for occasional access to solar images).
Slooh and iTelescope.net each have their benefits and advantages.
Slooh.com is unique for its approach to capture, but it has a larger focus on education and community. You can get high-quality pics, patience is key, and working within their framework can provide excellent results.
iTelescope.net is great too. You have nearly complete control of the telescopes and access to amazing telescopes and sites. The only overall drawback is sometimes the telescopes are busy, but a little patience helps and you eventually end up with quality images. In cases where images don't turn out well, their support is always available to help make things right.
iTelescope.net also offers its Master Classes too, which is unique.