I often see attributed to me the invention of the first "tri bike." But this company, Cervelo, is the first company to introduce what we, today, recognize as the modern tri bike. I might've developed a geometry used today, but Cervelo was the first to inject serious frame aerodynamics into a bike that also featured geometry that fit and handled nicely.
Cervelo worked out all its basic problems about a decade ago, when it simplified cable routing in its P2K, and added a chain stay adjustment screw to that bike's rear-entry, horizontal dropouts. Then it wrapped a seat tube around the rear wheel, the first time in the modern era a tri or TT bike has done so. That design is widely copied today. Then came the move to carbon. Since then it's been pretty clear sailing.
In this forward march offering feature upon feature, the P2 was, in a way, a step backward. Cervelo "unwrapped" the rear wheel with this bike—straightening out the seat tube—but, it didn't keep Chrissie Wellington out of the Hawaiian Ironman winner's circle (even if it was on a P2 frame one size too small for her). The P2 was probably the world's second best tri bike when it was introduced and, for some folks, a better bike than the better bike.
What makes the P2 possibly better than the P3? Geometry. No, it's really not any different than the P3 fundamentally, it's just that the P2 has a longer head tube than the P3 in its taller sizes. Today, your best play is to buy the most frame you can underneath you, that is, rather than a smaller frame and a longer, taller stem with spacers underneath, fill up that space with frame material (which is stronger, lighter, more aerodynamic, than stems, spacers, and overtall headset top caps).
For this reason, the P2 is a better bike for you than the P3, if the latter will only fit you with spacers and an upturned stem.
The P2 has been a category beater for years. At $2500 for a complete bike, nothing came close. But this bike isn't priced at $2500 anymore. For 2010, the complete bike price sits at $2800. And why not? It was probably priced too low at $2500. But, other companies now have bikes selling at this price point. The Cannondale Slice 4, Scott Plasma 30, Specialized Transition Comp, and Trek Equinox TTX 9.0, all sell for right at this price. Felt's B12 is priced only slightly above.
Has the rest of the world caught up to the P2? Yes and no. Specwise, the P2 is pretty much an Ultegra bike, and that includes chain and cassette, the biggest variances from Ultegra being the FSA brake calipers and its Gossamer Pro crank and Mega Exo bottom bracket. What's nice about the crank is its bolt pattern: 110mm, with 50x34 chainrings. This is the better option for most triathletes living in most locations.
Cervelo puts a Visiontech aerobar on the P2, with Vision brake levers and pursuit bar. What's bad about Vision is the lack of modularity and length adjustability. What's good about Vision is, if the bar fits you—if the right sized bar (for you) is on the bike—this is a nice, comfortable, ergonomic aerobar.
The P2 comes with boring, but eminently rideable, Shimano R500 wheels, and a Fizik Arione Tri2 saddle. Getting a good tri-specific aftermarket saddle on this bike is a big plus and, as far as the wheels go, boring is good. Sexy is bad, if sexy means a broken spoke at an inopportune time, with no way to run down to the LBS and get a replacement spoke stuck back into your wheel.
The spec on the P2 is superior to that on the Plasma 30 and the Transition Comp, both of those bikes featuring a largely 105 kit with an unimpressive Profile T2+ front end.
Is SRAM Rival a match for Shimano Ultegra? I don't know, but I think SRAM's Force and Rival groups need a few million aggregated consumer miles on them before we'll get a good sense for how it is they line up against Shimano's Ultegra and 105. Two attaboys for SRAM: its pursuit brake levers and bar end shifters. Shimano is still not out with a plug in brake lever (other than Di2) and it's still selling a thumb shifter decades old as its bar end shifter.
That established, neither Trek nor Cannondale is using SRAM's brake levers, and, this is one of the prime reasons for choosing SRAM for timed race bikes.
Finally, it should not go unmentioned that the P2 uses 3T's Funda fork. That's a high end fork on a midrange bike.
So, yes, the world has caught up in this sense: As bike companies aggregate models in and around this $2800 price point, you find other very nice frames—the Slice, the Plasma I, the Transition, the Equinox TTX, an un-bayonetted Felt—built complete. The P2 threads the spec needle a little bit better most others in this price category.
Because the P2 is spec'd with a low-profile Visiontech aerobar, don't let its slightly taller head tubes fool you into thinking this is a relaxed geometry. This is still a long and low bike ready for an aggressive position. If you don't intend to ride your tri bike reasonably forward, and, with a pretty flat back, the P2 may still work for you, but, perhaps a change of aerobar.