Of course there are tons of drawing Apps in the store ... it might take forever to try them all I guess it doesn't really help to have to have too many choices, good thing the selection is limited... LOL
I've over on the Surface Pro Artist site and forum asking a similar question. http://surfaceproartist.com/
The guy who runs the site has a list of the programmes that are most compatible with each version of the surface that should narrow down your options.
Then it comes down to what you want to do specifically as to what would best suit your needs.
Assuming your on a small budget like me...
Manga Studio / Clip Studio Paint (Same programme different name depending on if you get it on DVD or online) seems to be a good all rounder. All the drawing functions of Photoshop with out the photoshop price. Doesnt look that easy to use on the move though so i'd want something that was designed with a tablet style interface in mind.
Sketchbook Pro 7. Great for sketching not sure how far you can take your digital art with this though. Still researching into it.
ArtRage 4.5. Great for natural media and intuative user interface.
Black Ink. This one is new to me as I've only just heard about it. It was designed from the ground up to be a digital art package rather than replicate natural media. The custom brush settings look really interesting. It's available on Steam on sale at the moment.
I'll probably end up getting all 4 of the above in the order of preference listed but split each purchase over a few months as each seems to be around £35-50 (not sure in dollars).
I'm making a short youtube video review of 4 programs right now....ArtRage, Manga Studio 5, Photoshop CC and Sketchbook Pro 6.2.5. Hopefully that help you guys out, I'll notify when it's uploaded, or you can subscribe to my youtube channel. I'm trying to post one or two review videos every week as time permits.