From the information you have given I can't see any obvious reasons for refusal.
As you know the costs and risks are very low.
The decisions get made quickly.

Of course detailed timings on actual travel plans cannot be made and the ECO's accept this.
In fact the UKBA advice is NOT to purchase any travel tickets until the visa has been granted.
But there is a needs to outline the visit plans.
There is also a need for the sponsor to provide full details of support for the visit duration.