I have a subscription and do use it as a reference and to compare loads. As with anything on the internet, caution is advised, but I haven't seen anything outlandish. There are a lot of loads listed and it does provide a good quick basis for comparison. I'd be very interested to hear from some of the much more experienced loaders here too.
Have used it for a few years. All the data on it is from published sources. Various powder/bullet manuals, and also Handloader.com articles. I have a couple loading manuals (Lymans and Hodgden), but I really rely on Loaddata.com for my loads and comparisons. Then verify the loads elsewhere before I use them.
It's one of many sources and references that I use for potential loading data. I don't consider a load unless I can verify it in at least two, preferably three, reliable sources. Understand, of course, that the same load found in several places, referenced back to the powder manufacturer's data, only counts as one.
No one source for reloading data has everything I want or need... and even then I always seem to load towards the milder side of any given cartridge.
Like others who've commented, I subscribe and use loaddata.com as an additional resource. I may be a little more reckless than others, but since I primarily load handgun rounds I'll test fire them in my Redhawks if they look a little too hot...observing each one for overpressure. I think it's the best resource online...but again, just another tool that you need to apply common sense when using...just like when you use a hammer...