At first glance, many people are driven away from it. One reason is the artwork being unusual. There is also the aliens. an element that often drives people away and the summary of the story may sound a little cheesy. I myself considered it 'another badly made cartoon' only for it to become my favorite cartoon and story of all time.
The story is unique and what Savin Yeatman went through to realise his dream is very touching. What is most noticeable is the plot and the characters. Although due to the length of the story (only 26 episodes) there was too little room to develop all the characters. Nevertheless there are enjoyable and believable characters that you can sympathise and understand. Needless to say that Yeatman chose to have a female protagonist that can kick some ass. Meanwhile the plot has unexpected twists, in the races in particular. The Earth team actually starts out with poor ranks and barely makes to the second part.
There is a little bit of everything that can appeal to different tastes and ages. There are races, fights (physical and not), mystery (the aliens, the planet),emotional parts and love.
I believe the lack of funds which resulted in a short series was a bit of a drawback. It isn't bad but considering the information found in the Art of Oban star racers it seems that Yeatman has gone deeply in the universe of this series, there were many things that could be added to the episodes. The fact that there are a variety of races opens up roads for content. Also, because of that some events occured too fast (Molly gets attached to Aikka too fast considering they barely got to do things together like she and Jordan). Despite that, I'm rather happy with the way the episodes wrere done. No minute was wasted. The dialogues are rather well written, if not one of the best I've seen (might be biased here). Once the series is over, you will want more...
It's worth to mention the design and overall concept of the planet Oban. The explanations sound rather 'logical' and believable while the scenery simply leaves you in awe.
To put it in a nutshell, it's a unique and well-done series. The creator has put a lot of love into it. It has it's flaws (mostly speaking about the pace of some events) but can be easily ignored. You will either be driven away for it's 'weird' stuff or fall in love with it.