Who doesn't like Vallis? If I cast my mind back it was one of the first plants I grew extremely well by doing...nothing. In fact it grew like a weed and provided a wonderful curtain effect that made me feel like a pro :) I'm not sure which specific Vallis it was but it was dead easy. In fact the entire Vallis range is very simple to grow and unless you have very soft water you won't have any problems.
There are currently 5 different types available - all similar (ish) with a variant. Let's start with the biggest first:
Vallisneria gigantea rubra - large thick and wide leaves that grow fast. Great for bigger tanks and the leaves can grow up to about 2m (impressive heh!).
Vallisneria spiralis - suitable for beginners and up, this plant has narrow long leaves that look rather attractive. Grows in pretty much any tank.
Vallisneria spiralis red - just like the plant above but with a red tinge. A bit slower growing though.
Vallisneria torta - the smallest of the Vallis, this rather neat one tends to stay quite small as the leaves twist as they grow. Also great for beginners and up.
Vallisneria nana - the narrowest of all the Vallis, the leaves are a few mm thick. This makes them sway delightfully in the current. Not such a fast grower but very easy on the eye.
Just in case you're not aware, Vallisneria do not appreciate liquid carbon. It can make them melt so best to avoid adding it.