Positives: Kanter is a big guy. He is a very built 260 pounds and can throw his weight around well. This helps him in the offensive post and to be a dominant (at times) rebounder. He his post moves are fairly well developed and he is a very offensive minded Center. He is a very solid shooter and can step up and knock down the midrange. He has big, soft hands that can help him rebound and receive passes in the post.
Negatives: He is not particularly athletic and his physical ability limits his upside. He has an average (at best) wingspan for a Center at a bit under 7'2''. To couple with his average wingspan, his jumping ability is a tick below average and he will have to rely on hustle and strength to grab rebounds. There may be character questions since he had to miss the whole season at Kentucky and he has also had injury problems in his past. Still needs polish, only having played a year in High School.
Comparisons: Chris Kaman (best case)/Nick Collison (worst case)
Why the Cavs should draft him: The Cavs need big men. Chris Grant has stressed this as a big focus for the draft and its clear they need depth. They only have one real "true center" in Semih Erden and he is more of a true center than Varejao. Even though he is unpolished, he is considered one of the safer picks.
Why the Cavs shouldn't draft him: Limited upside. There are three types of players you generally want to draft if you can't get an elite pick: guys who need polish but have a lot of upside or guys who can contribute right away but have limited upside. Unfortunately, it will likely take Kanter a couple years to contribute significantly. He also may not be a true center and the Cavs have enough Power Forwards.
Verdict: I favor other players at this position but if they are gone, he is a suitable pick. I think he will end up being a good player, it may just take time. He played only one year of HS ball and one year of pros in Europe where he averaged 7.8 minutes a game. Guys like Chris Kaman and Al Horford (who he is similar to) took a few years to develop and these guys played all 4 years in college and were considered more pro ready. He will end up being a solid player eventually, but his ceiling may be Chris Kaman and more likely, its Al Horford (15/9 guy with above average D and soft hands).