I'm new to mountain biking. I rented and tried out several bikes before buying a Kona Blast. Generally, I really like the feel of the bike, although I think that I might prefer a less upright riding position. It's a 2005 18 inch model with 100mm fork. The dealer switched out the stem to the longest one that Kona had provided to him with his opening order. The stock bars have a gradual rearward and upward sweep to them. I feel like a straight bar would help me stretch out a bit more, providing a more aggressive head-down position. Are there any other advantages or disadvantes to this modification that I should consider? Why do so many factory bikes come with bars with an upward/rearward sweep? Thanks in advance.