Hello Geo123,
I've checked the CRA entries my T5008 slips are complete.
In the past I've used the download as a check to ensure I've entered all required slips. To be fair, this has been more important for T3's and T5's because in several cases I get paper copies only and in others I only find them on the CRA site.
I've been using UFile for about 10 years. Given UFile's response to this situation. I'm not so sure I will be doing so next year.