I´ve ridden the southern section of this route and it´s excellent; especially the D918 west from Arreau. Arreau itself is a pleasant spot for a teabreak before you set off. There´s also a restaurant on the Col de Tourmalet.
A few warnings: There´s a lot of two-wheel folk around, so be aware; keep an eye out for gravel wash in road on the Arreau-Col d´Aspin section and remember to check the cols are open before you set out.
Other than that this is an unmissable ride if you´re in the area.
I more or less am living in that area.I did the Cols dAspin and Tourmalet many times by car and bike. The views from those cols are great ! This is a classic tour trip in the area which is really worth it !
D918 Arreau-Col dAspin
Col du Tourmalet