There is nothing wrong with self-upvoting. In fact, Steemit sets it up such that the default option when you publish a blog post is to upvote it. Knowing that you can earn a Dollar a day (or whatever amount it is) simply by upvoting a bit of your own content is a great motivator for investing in Steem Power, and lots of people investing in Steem Power is good for everyone involved.
Having said that, there is already a vague unwritten rule that too much self upvoting is tacky and people do notice and so I think that can work against you.
The other consideration is that self-upvoting at the expense of upvoting others is short term thinking. Most everybody who has prospered on Steemit has done so by networking with other people and being generous with their upvotes on other people's content.
Although the system itself is engineered to allow for self-upvoting, the social component to Steemit does a very good job of limiting it.
I'll upvote my own comments if I want to and you can feel free to not upvote them if you don't want to.