That entry level bike is good enough to win major races. You will be making nearly no compromise in performance with it. Tiagra is excellent stuff - don't believe the 'Tiagara and Sora sucks' crowd - they're niggling over details.
The usual caveats about buying online as a new cyclist apply, regarding fit, and troubleshooting, but odds are that this will be a good bike for you. I'd still check out the LBS though - today's crop of entry level bikes for $700 at the LBS (realistic price there) is very impressive, plus you'll get good handholding from a good LBS, and perhaps the most important aspect - the LOOKS of the bikes are far superior to the Motobecane entry level line, which are, frankling uber-boring.
Sounds trivial, but this is true - do NOT underestimate looks of your entry level bike - I think it is the single biggest determining and differentiating factor at this pricepoint. Discounting online vs LBS differences (BD is the lowest price, because its online), the components and quality of parts is essentially identical for new bikes, and not worth comparing. You get more meaningful part differences at higher price points, between groupsets, wheel differences, etc., but at entry level, it's almost all nearly identical.
LOOKS are the critical factor, and you'll love when you hop on a bike that looks great (it will ride great no matter what if it fits reasonably well.) I love the look of today's Secteurs and Trek 1.1s, and this is coming from someone who owns a Cervelo (as well as an entry level Giant, so I can speak from both hi & low end perspectives.) In my opinion, frame quality and looks has been the biggest improvement in entry level bikes in the past few years - I think previously, manufacturers intentionally kept entry level frames 'boring' because they didn't want to cannibalize their hi-end bikes (it doesn't cost a whole lot more to make a good looking frame if you've got a die for a good looking higher end bike already), but now it's competitive enough with frames direct from China that they're designing the entry level with great looks as well. They hang hi-end dura ace and ultegra off those exact same frames (like the Trek) and sell them alongside their top-end bikes at hte LBS.