Gamaran is awesome because the author sticks to what he does best - well drawn, exciting, old-school fight scenes made even better by being believable. The pacing is fast, so if you're reading it straight through you really start wanting a breather with something slower. But I can also see how this would be great if you're reading on a weekly basis; you'll know that Gamaran will always deliver.
Artistically, some characters start to blur and he's not exactly breaking new ground stylistically. Gamaran really shines when it comes to storytelling and panelling. Everything is clear and concise, even in the middle of a complex fight scene.
Plot-wise, the beginning was very typical shounen. Young lad sets out on journey to kick some ass, powers up to kick ass, etc etc. While I did enjoy this because the author was very blunt about what the series was about (the tournament was unpretentiously about whoever was the strongest), the constant fights were definitely getting old after a while. But since the timeskip (chapter 84,85), things have gotten a bit more complex with intrigue, betrayals, etc. Now I'm actually interested in reading about something other than fights in this series.
There's somewhat of a lack of deep insight into characters' motivations and feelings beyond what you would generally find in shounen. I'm of two minds with this - it doesn't make for memorable characters, but there's also no wishy-washy moralising.
In the end, I like Gamaran because it's unpretentious. It's purely about awesome fights. If you want anything more than that, look elsewhere.