They were a nice addition, and something I am glad they kept in the games. Yay for not needed to walk slowly!
One thing still bugs me about it though - and that's having to hold the B button. It's something they fixed in HGSS too and then unfixed, so it's something I hope is rectified in later games. After all, having to hold the button for all that time was kinda annoying.
Otherwise I... don't have that much opinion on them. Nice until the bike/indoors in later games, but that's basically all there is to it.