The DLCs are good.

Get the GOTY. The DLC add to the game and are fun to play.

ty now im ready for the steam sales :)

Yes, DLCs add lots of quests, completely new big locations (not as big as Washington wasteland of course), items, etc. For example, events from Operation Anchorage DLC are going in the snowy location and are organized very specifically. I don't want to make spoilers :) Max level is also raised from 20th to 30th. Totally worth it. But better wait for the sale. It was already 75% off several times.

Yes it is

YES.

Well if you get a really good deal... But technically speaking you could get the base game and grab the DLCs from another source coughfriend/torrent/etccough since the game treats it as a mod.

I never played Fallout 3, only New Vegas. My problem with the goty/ultimate edition is that they always put the base game at -75%, the goty/ultimate at -60% and the dlc at -40%. Maybe not these exact values but you get the idea. And I don't support that. What I can say, however, is that the vanilla New Vegas is extremely fun and big on its own. The only downside is some good mods require all the dlc. But it's no big deal, really. There are TONS of amazing mods who don't.

Yes, because of broken steel. 10+ levels, new perks, a little bit of story (with actually an ending). The other DLCs are good. Point Lookout has a great map and The Pitt a good story (imho). Aliens is a LOL, weak DLC with a litltle parody.

In my opinion, is GOTY or nothing. The same with New Vegas.

Also, most and better mods requieres GOTY / Ultimate.

I also recommend the full extra edition.
I have GOTY at DVD format, but Steam didn't accept the serial :[ Extra money now to have it in library.
Also, I still support F2 as the best game of the franchise. I would love to see for example nowdays, a new Fallout with Wasteland 2 or better graphics.

YES

Looks like you already have your answer but +1 for GOTY!

Goty is love, goty is life.

Yes, Dlcs are very good also once you finish the normal game with the dlcs you have the option to free roaming and keep playing/exploring.
If you finish the game without any dlcs you can't do anything else.