Hey DR (and anyone else), the bike shop here sells Trek, Specialized, and Cannondale. In road bikes they are pushing the Specialized. The story I get is more comfortable geometry and better durability in our harsh (salty tropical) conditions.
So I am looking at the Allez and Allez sport as my first trainers. Do you have an opinion on those bikes, how they compare - say to the Trek 1.2, or any considerations I should make for this purchase? I imagine I'll be riding 100mi a week or so.
Agree with DR, at that price point the Canondale CAAD range is my fave, good frames for the money. However there's not a big difference in quality between the entry-level models of any of the major brands. The CAAD9 has been discontinued though, so unless you can find one 2nd hand you'll be looking at a CAAD8 (or CAAD10 if you splash the cash).
The most important thing is to chose a bike that fits though, not whatever's cheapest/ looks best/ is being pushed by the shop. Make sure you test ride and get multiple opinions about fit if it's your first road bike. Don't be afraid to ask for a second opinion on fit, or even better go to another shop for a second opinion. There's minimal difference between the geometry of the current Allez and CAAD ranges, so you should test another brand as well. You'll be happy with whatever choice you make as long as the bike fits you.
Compact chainsets are universally preferred over triples these days unless you're touring.
I doubt that your local shop is changing out any of the standard components, regardless of local conditions. There's usually not enough margin to do this. If you live near the coast you'll need to make sure to remove and regrease bolts regularly, keep the bike dry and indoors, and wipe the transmission at least weekly. The benefit to buying off-line is that the bike is generally put together with a bit more care, you get better sales advice and after-sales care.
Spend as much as you can afford because marginal gains are pretty good at the entry-level price point (unless you're intending to upgrade the bike in the near future). But remember to save some cash for accessories - helmet, shoes, pedals, bibshorts, pump, tools etc. don't come cheap! You may want to swap the saddle and tyres soon after purchase also, these two items make the most difference to ride quality/comfort, but again not cheap.
Don't be afraid to ask for a cheeky discount! Most shops can do >10% off rrp on the spot. If you're buying accessories also then ask for a bunch of free items instead of a discount - shops can accommodate this more easily because of their mark-up. Push the fact that you live locally and can provide repeat custom to help generate goodwill. Shops love regular customers and you can build up great discounts this way.