I'm cautiously optimistic because I want to see all they've learned since GTA4. Personally, while I liked euphoria when it first came out because it was neat, I have actually grown to abhor it because it makes the entire game one slow, tedious process, though it was mostly fine in RDR.
I know what you mean, though. I think GTA4 is too front loaded for its own good. I thoroughly enjoyed, even flat out LOVED the Broker part of GTA4, because it was like opening Christmas presents on Christmas Eve -- hey, a fresh new GTA to play through! But as the game continued on, I started to realize I just wasn't having as much fun as I did in past games and by the end of the game, I completed it just to complete it. I just wanted it to end.
I got GTA4 and the expansions last year for ps3 and I too, was reminded why I'm just not a big fan of gta4. I think TLAD fixed most of the issues though, because of the emphasis on bikes, which don't feel like you're driving a motorboat on greased tires. I couldn't even get past the Broker section and returned both the expansions and gta4 proper after completing both tlad and gay tony. I got burned out just by playing two expansion packs.
That said, I gotta give credit where credit is due. Rockstar North seemed pleasantly surprised by how well RDR turned out and maybe they even have taken notes from games like Saints Row.