Ignore the people telling you to wait for a price cut. Just get it now. The price cut may or may not happen, and it will more likely than not take out several features.
MGS4 and Uncharted are very good choices. If you can get one more, I recommend LittleBigPlanet. Killzone 2, Valkyria Chronicles, inFamous and Tools of Destruction are also must own exclusives. For the rest of this year, keep an eye on Uncharted 2, and R&CF: A Crack in Time, and MAG and GT5 if they appeal to you.
I say all this with the assumption that you already own most of the great multiplats on 360. Though if you are planning on getting any MGS, Final Fantasy, Tekken or DMC game (or anything which was once a Sony exclusive), I strongly recommend the PS3 version- it will usually be superior.
(Former) Lead Moderator and (Eternal) VGC Detective 
