I'd tend to disagree with Marcus and say fit on a road bike is very important, esp in comparison to a mtb. On a mtb you're in and out the saddle and constantly shifting position, on a road bike you can be sat relatively still for most of the day if you're out getting some miles in - any issue in fit will really show up then!
There are a few methods for determining road bike fit, think the
Lemond method is a good starting point. Goes without saying it's worth seeking advice in a good LBS.
May have totally gone off the point here, not sure the OP asked on fit! Oh, that planet-x looks like super value also.