I have actually found them very helpful. There was a case, recently, when the landlady was away on holiday so did not provide a reference. RentGuard failed the referencing because of the lack of landlady reference. However, when the landlady got back in touch, they sent over a new report which passed the tenant. The referencing is based upon the information they are given, and they certainly tried a number of times to make contact. So a failed report, doesn’t mean the end - it means you need to ask why (and it clearly said in my report that there was no landlord reference).
I have also had refunds from them when I wanted to cancel referencing (and they’d started the process) both by calling them, and through the open rent site (when tenants didn’t do the online agreement for the referencing)
We also have the RentGuard insurance, so passing reference is a requirement.
As always, I think people are more likely to go and complain on a review site, than they are to praise a company. Since the referrencing company don’t harass us with “please review us” every time, it is just those with a gripe that tend to bother with the reviews. Give them a try, and if you don’t like it this time, go elsewhere.