What do you like best?
Allows pre-screening candidate profiles and aptitude before investing large amounts of time in interviewing, etc. Easy to use as a 1st step to separate the wheat from the chaff.
What do you dislike?
Would like to see some better customization options in testing (e.g. DiSC profiles, etc.) and also would like to see e-mail integration so that e-mails send from user's Office 365 account rather than a generic account. I had more than one e-mail intercepted by SPAM or just never went through. Read Receipts would also be nice.
Recommendations to others considering the product
Be sure you take the time to properly configure the testing for each role. I found that the Typing Test is a really good indicator of how quickly someone can think and work - whether the role is technical or not. I recommend always testing their typing skills to get a baseline and see if you find the same to be true (I'd usually look for 35 or better - their test is WAY tougher than other typing tests IMHO, so keep that in mind). I'd also suggest taking each test yourself to get a benchmark.
What business problems are you solving with the product? What benefits have you realized?
Reduce time spent pre-screening candidates. It takes a little time to benchmark and really "trust" the testing, but sometimes they can be great indicators. Never 100%, but definitely a good thing to take into consideration. If someone bombs everything, it is more likely than not that you'd be wasting your time if it is a position that requires the skills tested.