.. c5 in Queens Gambit Declined I've been playing c5 as black in Queens Gambit Declined lately.

i.e.

[FEN ""]
1. d4 d5 2. c4 e6 3. Nf3 Nf6 4. e3 c5


I just want to know, how bad an idea it is to play in this way? I saw someone play it in bullet game but I don't know when it's best to play.
The move 4... c5 is good because:


It is thematic in the Queen's Gambit Declined to break with either ...c5 or ...e5. With 4...c5, this is done without loss of time
White isn't putting pressure on the centre, so Black can take it


Here is a sample game, which ended in a draw, between top players Karpov-Sveshnikov

[FEN ""]
[White "Karpov"]
[Black "Sveshnikov"]
[StartPly "8"]

1. d4 d5 2. c4 e6 3. Nf3 Nf6 4. e3 c5 5. Nc3 Nc6 6. cxd5 Nd5 7. Bb5 cxd4 8. Nd4 Nc3 9. bxc3 Bd7 10. O-O Nd4 11. Bd7 Qd7 12. cxd4 Be7 13. a4 O-O 14. Qb3 Rfc8 15. Bd2 Rc6 16. Rab1 Rb6 17. Qa2 Ra6 18. a5 Bd8 19. Qb3 Ba5 20. Ba5 Ra5 21. Qb7 Qb7 22. Rb7 Rc8 23. Rfb1 g6 24. h3 Rc2 25. R1b2 Rb2 26. Rb2 Ra1 27. Kh2 h5 28. g4 hxg4 29. hxg4 a5 30. g5 a4 31. Rb8 Kg7 32. Ra8 a3 33. Kg3 Rg1 34. Kf4 Rg2 35. f3 a2 36. e4 Kh7 37. Ke5 Kg7 38. f4 Rb2 39. d5 exd5 40. exd5 Re2 41. Kd6 Rd2 42. Kc6 Rc2 43. Kd7 Rd2 44. d6 Rc2 45. Ke7 Re2 46. Kd8 Rd2 1/2-1/2