Even a really well made guitar can never be totally in tune all the time - specially up the neck - it's always a compromise. I have two 'big' Martins which are regularly set up by an expert pro, and I still have to retune every string when capoing - even if only on the third fret. Baby and travel guitars will suffer more, both because of the short scale and the thin strings advised by the makers.

As for capos - I'd suggest you avoid the G7 if you play gigs. I know SO many people who've had them fail suddenly. I got through three in quick succession myself, ruining a song each time. Now if I see them in a shop I tell the guy not to stock 'em! :-). Shubbs are good, but they have to be just so - with a twist to the wheel for every fret. What with talking to the audience AND tuning all six strings, AND remembering the intro to the next song, that's quite enough multi-tasking for one intro, thanks! I went back to the Kyser in the end. You can tune through them, they're never over-tight (major problem with Shubbs), and they always fall square on the strings. Thin too, and the most out of the way of your first finger (Dunlops are thin, but not strong enough for the larger Martin - tend to buzz).