We have a G-Luxe too, and like it a lot (especially me, because I'm ~6 ft tall and walk fast which means that I dislike Maclarens b/c the back crossbars get in the way of my feet).

It has been our daughter's only stroller since 10 months or so. But I'm not sure that it would work for a 4 1/2 month old. Both size and neck/head/body control could be a problem at that age.

One sidenote: if you do get a G-Luxe or G-Lite, be sure not to leave the coffee cup holder on when you gate check it. We lost ours that way, and somehow can't bring ourselves to spend $20 for a replacement from Uppababy.