I've owned my G26 for over a year now. The gun is a joy to shoot, and is surprisingly stable for its size.
The A&G mag adapter (attached directly to the magazines lower body) I got so I could use full sized G17 mags gives the G26 a really good feel. Glock claims you can use the G19 and G17 mags in the G26, but without the A&G adapter you may run into a lot of feeding problems.
I would get a set of night sights if you didn't order your mini Glock with them. Like all glocks, excessive holstering will rub the plastic sights (stock) down to nubs in no time.
Meisterman, I think the +2 extensions would make the grip akward. You would also have to custom cut a 'full size' mag spring in order to make the +2 extensions work reliably. Not a problem with the full sized mags cause you can get "power" springs for those that are longer than the stock springs. Oh, you can still get power springs for the G26, but they look a little too short.
A Shok-Buf would be good tto. Hope this helped,
E