One feature of ProZ that is surely notable and it’s also quite estimated by its detractors (as well of course, as the people that like the site just like me), is The ProZ.com Blue Board.
The Blue Board (for short) is the Tripadvisor equivalent of the translation market for freelancers, where you can find agencies and see how well are ranked by fellow translators. In particular, the criteria used encompass five different aspects.
(E) Easy/enjoyable to work with - For example, if an agency you worked with has particular accommodating workflows, and the projects are clearly defined.
(Q) Considers quality - Not all translation agencies consider quality on the same level as others, and this aspect can be particularly crucial for translators out there, as we’re often deemed to be perfectionists.
(O) Straightforward onboarding - Some agencies, particularly bigger ones and others who love bureaucracy (I don’t), tend to have overcomplicated onboarding processes. Not a big point in favor.
(T) Adheres to terms - Agencies are notorious for making you sign (sometimes) long NDAs and PDFs on PDFs of contracts, just to not respect their terms. This is particularly true for payment terms, where companies tend to delay as much as they can the day you’ll receive your money; this is also linked with the next aspect.
(P) Reasonable payment terms - Agencies usually have 30 days of payment terms, sometimes at the end of the month, sometimes as fixed (30). This is by itself still quite a lot of waiting, and some others go as closer to 15 days (yet to find one!), or, terribly enough 45/60/90 days even!
From how I see it, The Blue Board is a valid tool to intelligently make guesses about agencies' integrity before starting to work with them. We can see if they pay on time (some agencies are even banned from ProZ when they don’t pay translators in batches, and this can result in them taking rightfully lead and creating movements over the Internet, which can sometimes have positive effects on the work done getting correctly recognized, hence paid. I’ve seen this happening lately on LinkedIn in regards to a particular gaming agency, notorious for not paying translators.
What ProZ.com also does with The Blue Board is assign an average score (from 0 to 5) to the agency based on the entries submitted by translators who worked with said agency. This is not dissimilar to what happens with reviews on Amazon, or your favorite app store for your mobile phone - it’s the same base concept, with stars and everything.
What you can also do to further check an agency's quality, before applying, completing onboarding, or accepting tasks with them, is see the job posted by the agency and their nature: if they’re posting a lot of jobs in a short period with the same tasks and requirements, it’s likely that they’re not finding people of the job, and something’s off - either they charge really low rates, have unbelievably high requirements (rare instance), or something in the onboarding process is not clear or good enough a reason for translators to stick around with the agency.
Another thing you can check is to see the rates (if available) posted under the job descriptions. While it is true that you can try your luck and see how much they charge translators by looking at the quoted price on the translations via their website, this is not always feasible. Sometimes you have to wait for the agency to get back, and this requires time. Checking job descriptions can also give you a clearer picture of the kind of jobs the agency hires for.
Also remember to check, of course, WWAs given to see if the agency in question recognizes the effort of their translators, and you likely have the chance to receive a nice 5/5 star ranking for your efforts on ProZ, or at least a well-worth thumb up.
The analytics tab (which I’m not sure if it’s available to non-Plus or non-paying members of ProZ is another beast. It will let you check interesting stuff like where the reviews come from (if they’re verified - you never know! -, the countries where they come from, the age of the reviewers’ account, etc.
Generally speaking, I’d say other translators’ reviews are quite valid, and to the point. If you see a company with less than 4, you probably won’t want to work with it, or at least check more carefully before delving into contracts with it.
Be extra mindful of comments from translators mentioning the agency is unwilling to pay, or if they drag on with the payment terms. Big red flags!
I hope this overview and insight on The ProZ.com Blue Board was useful to you!