My opinion is that any bike is good for a starter bike as long as you can handle it properly and are confident on it.
I've had spills on 50cc, 250cc, 660cc and 800cc bikes. Luckily not in contact with other vehicles, which I reckon as the most dangerous. One has to be vigilant to no end on public roads, be it on a scooter or big bore bike.
The XT660 is not a overly powerful bike, but faster than most 250's to get away from traffic when needed. I ride a lot in the city and despite the height of my XTZ, the bike handles exceptionally well and is quite forgiving when you do make mistakes.
The XTX is lower and a very good handling bike too.
I'd say, go for it, enjoy and be safe - take it easy
