I've watched about 100 eps now, and I like it. If you know what to expect, Prince of Tennis will deliver. If you want to judge the series in a fair way, watch more than 10 eps. I was about to quit watching it after a few episodes, but I continued. It's slow in the beginning, but it'll pick up. And when it does, you'll have a lot of Prince of Tennis goodness to look forward to.
Since the main character Ryoma Echizen already IS really good from the beginning, you won't find the same "success story" as in Ippo for example, at least not to that degree. But PoT is good in its own way IMO. Even though Ryoma is good, he'll face fierce enough challenges. Despite the name, the series isn't focused heavily on Ryoma either, it has almost equal focus on the other club members. Since they play tournaments as a group, it's about the team rather than just Ryoma. And yes, they're not perfect players, and they WILL lose some games.
Anyway, Prince of Tennis has those really tense moments, funny moments, and good characters. After a while the series has grown on you, and you'll continue to watch it.
There are some bad sides though...some of the filler episodes aren't that exciting (I completely skipped those silly chibi episodes, for example), and some things that are repeated throughout the series can get tiresome (at least when they appear frequently). But I still recommend it, very good series.