Most certainly play it, but mod the fuck out of it...
There's a lot of gameplay imbalances when compared to Fallout New Vegas, and you feel completely unstoppable by the mid 20 level. Unlike in New Vegas when Deathclaws still pose a challenge at max level (level 50) even. You can remedy this, by modding the various mechanics, like perks every two/three levels, or changing the stimpacks so they recover gradually. It makes the game more challenging, and more of a survival experience, akin more to the original games. If you want to go even more hardcore try the Fallout wanderers edition, which is similar to hardcore mode found in Fallout NV.
The Ironsights mod is a must, and adds a lot more dynamic to the shooting like it did in NV. Also Fellout removes the ugly green tinge to the graphics, making it look much better. Project Beauty is also a great mod that makes everyone's faces not as low poly and ugly looking.
The DLC's are a bit hit and miss in Fallout 3, unlike NV, which i found that all four were great in their own way (Yes even Honest Hearts, screw the haters!). Broken Steel, Point Lookout, and The Pitt are worth it though, especially Broken Steel, because it raises the level cap, gives you more late game content, and has more tougher beasts to take care of.
Mothership Zeta is total rubbish, and doesn't make sense at all in the Fallout Universe (though the Alien Laser guns are cool as hell), and Operation Anchorage is a boring three hour linear path to some really broken loot at the end, that completely destroys the game's balance (stealth suit is far too OP, a 100% sneak skill...yeah).
Overall...i find Fallout 3 to be a good game, but not a great fallout game. The dialog and characters (which the originals and New Vegas excelled at) are not memorable in the slightest, and if you want a good story you won't really find it here. Though if you want pure and utter atmosphere in your Post-Apocalyptic games that you could cut with a knife, Fallout 3 has it in spades, which even New Vegas lacks.
Also one thing of note, the speech system in Fallout 3 is absolute pants compared to NV. Going on a percentage to your skill points, rather than a required points system like in NV. So there's not really much point putting too much points into speech, as speech success boils down to luck pretty much (and if you are not successful you can just cheat and reload). In Fallout NV speech is one of the most important skills to have.