Let me say right out of the gate that I would gladly take all of the "downsides" that I'm about to list in exchange for a Super Bowl trophy. However, there are some negatives to making the playoffs in the current NFL (that is, one with an uncapped year in 2010), and especially for being a "final 8 team. Here's the summary:
There are restrictions imposed on playoff teams like Dallas and Philadelphia in terms of how much they can spend on free agents and their negotiating access with free agents in general. There’s a lot of technical minutiae, but the most stringent of these restrictions applies to the final eight teams in the playoffs, known as the "Final 8" rule.
As Kirwan notes: "The rule will restrict the final eight teams in the playoffs from signing free agents. The final four teams shall not be permitted to negotiate and sign any unrestricted free agent to a player contract except for players who acquired their status by being cut or were on the final four team when their contract expired. Playoff teams five through eight get a break to sign one player with a salary of $4,925,000 or more and any number of players with a first-year salary of no more than $3,275,000 and an annual increase of no more than 30 percent in the following years."
Here's the link for the full breakdown of the uncapped year ramifications:
Basically, there aren't going to be many free agents to spend money on, and if you're a "final 8" team, then you're not going to get much of a shot at them unless you have a lot of your own guys leaving.
The way I see it right now, we don't have many guys leaving this offseason, which is a great thing, but limits our FA ability a bit. I believe our notable FAs will be Barbie and Sensabaugh. I think Miles Austin gets captured by the uncapped year stuff and doesn't turn into an actual UFA. But I could be wrong, I have not looked at all of our contracts in detail relative to this uncapped year language.
All in all, it's a problem you want to have-- regular season success, a playoff berth, and not many current players looking at free agency. But it will result in some limitations being imposed on us.