One of my bikes is a Specialized and it's a good bike that does everything I need it to do (group rides mostly....I'll be doing a few crits until tris start in March as well) with very few problems. That said, I think Felts are better built, but still very little difference. What is most important is that the bike fits well and is comfortable. If you're going to be doing longer rides, comfort is extremely important.

For components, the biggest difference between 105 and DA is going to be the weight. You'll probably save about two pounds going with the DA. Also, the shifting will stay crisper a bit longer, but as long as you stay up on the maintenance, this will be much less of an issue than many people make it out to be. If you don't want to learn to do derailleur adjustments, your LBS should only charge about $5 to do it. My training bike has Sora/Tiagra, and as long as I re-adjust it every few weeks the shifting stays clean--a good bit mushier than my good bike, but still clean. Another thing to consider that has varying importance to people....generally more-so for roadies and less for triathletes....is style points at group rides. Some people care a lot....some not at all. I judge on how well someone pulls in rotation, but there are plenty who care about what you ride (sad but true). But as long as you put the effort into keeping the 105 set adjusted it will perform very nearly as well as the Dura Ace.

As for cranksets, if you're going to be riding up some super-steep hills, the triple might be nice. Here in Florida, where it is affectionately known as the "Granny Gear", we don't get much use from it. A compact will let you spin easier, but if you go fast enough it is possible to run out of gears (usually at about 29-30 mph if you want to push a low cadence, which is easy to do if you're drafting in a big enough group). You can fix this a bit if you need by getting a cassette that has an 11-tooth small cog instead of 12.

As for shoes, as long you aren't racing Cat I/II, weight really shouldn't be an issue. As long as the sole is plenty stiff (so you get the most power transfer to the pedals) and they are comfortable, you should be ok. If you intend on getting competitive with tris in the future, you may want a tri-specific shoe that lets you do flying mounts (one strap that opens away from the drivetrain). Otherwise, cheaper shoes shouldn't give you a problem as long as they're comfortable. When you get pedals, a lot of people think Speedplays are the stiffest, but they're hard to walk around in since the cleats are so bulky. So if you do tris and don't do flying mounts it'll be easier to trip if you're not carefull. I think the best value are the Shimano SPD 105's. Plenty stiff and only $85. I'd stay away from the metal MTB pedals Shimano makes. I bought them at first to save some money, but after a few months, the cleats were destroyed and I had warped the pedals doing sprints. As soon as I switched to SPD's, I noticed how much stronger the base of the pedal felt and the difference in the power transfer was incredible since there's so much more area in contact between the cleat and pedal.

Sorry this was so long, but hopefully between this and whatever other people can add with their experience will help you get what fits your specific needs. And btw, both are really good deals. I just bought an 06 Scott a bit ago, and realized that I had fallen in love with end-of-year clearance sales!