Well when I saw Varus I began saving up my IP so I could get a new ranged carry to add to my collection of champs. When he came out today I immediately bought him, but with exams coming up I've had a chance to play him twice.
That being said, here's my input:
His AD to autoattack is decent. By far outmatched by Ashe, Cait, and Vayne - even other AD range like Twitch and Teemo are going to have a much better auto than Varus. In exchange, Varus has abilities tailored for burst damage; his W, in combination with an opening Q, can really devasatate an individual opponent. In reality, Varus isn't about stacking damage for a rediculous auto, its about getting damage with some AP to attack in bursts. Unlike Ashe or Cait, Varus can use all of his abilities in succession to burst a single opponent. After applying a few stacks of blight, an opening Q, followed by W, followed by more stacks of blight, another Q, R, etc. allow Varus to lay waste to an individual champion. His autoattack is more of a sustain between abilities - useful for stacking blight, as well as maintaining a steady drop in enemy HP.
That being said, I see Varus as kind of a ranged form of jax; he's got a lot of range, with some stuns and slows, all of which depend on a good balance of AD and AP to deal enough damage before an enemy can get away. However, as Varus is ranged, he's obviously much more squishy than a hybrid like jax, but the tradeoff is that Varus can take down enemies safely from a distance.
I do feel the Q costs a significant amount, especially when its so vital to early lane harassing. That being said, it's also similar to Blitzcrank's Q - if the cost weren't high, spamming it would be OP, and the enemy wouldn't have a chance in lane.
What'll seperate a good Varus from a great Varus is item build; going pure AD and relying on autoattacks won't cut it. The only problem is, where hybrids like Jax can get away with doing a hybrid AD/AP build, Varus is squishy enough to where he has to chose between getting some AP to make stacking blight and his ult worth it, or getting surviveability items like warmong's or banshee's veil. Hybrid builds work well on Jax because of his built in defense abilities, and the fact that he's a fighter with decent health and armor/mr to begin with. Jax can afford to ignore buying defensive items early game; spell vamp and auto vamp aren't enough to save Varus if he gets focused.
It'll be interesting to see what builds come up for Varus, but he's still a fun champion to play and I'll keep tinkering with him until I find the right fit.