It is an acceptable SEO figure for a new business that is just 5 months old. I mean it takes reasonable time in generating brand development and product awareness. Getting 9000 visitors is a good score IMO considering the age of your business and employment of SEO techniques. But there are some relevant questions that may give you a performance outcome of the SEO efforts like;
I hope answering these questions can help you measure and track the effectiveness of SEO person in the real time. But I will advise you to have patience because SEO is a slow treatment. But it is one rock-solid and effective resource that can bring lots of dedicated traffic from natural sources for a longer period of time.
You have to ask two questions:
1) Is the traffic coming from an audience you want to target?
2) Is the traffic turning into sales?
If neither of those is happening then you're likely just doing an excellent job of wasting bandwidth. Raw visitor counts are pointless and are frequently used by less scrupulous SEO experts as smoke to disguise whether they're actually being effective.
It depends. Did you meet your sales goals with the traffic your blog got in the last 3 months ? The purpose of SEO is to create buzz, so your website will be ranked as high as possible when searching for specific anchors in search engines. that's the only way to verify you're getting got quality SEO work. If you want more traffic, consider envesting in PPC ads.
As Joseph said part of it depends on your market potential. If it is a small market then 9000 is great. If it is a huge market, then 9000 doesn't sound too crash hot.
Another factor you need to consider is the level of your competition. If your industry is extremely competitive and small 9000 could be a great feat as well. If it is large and not competitive then 9000 isn't really that much.
The question is really too broad to answer without specifics.
Impossible for us to say without understanding the potential size of your audience. It all depends on your industry, your offering and your goal.
A better question is whether it meets your expectations. You hired an SEO in order to drive organic search traffic to your website - how much traffic did you have in mind? Ask yourself:
Try to understand yourself how organic search can benefit your business. Think of the kinds of things people type into search engines when they are looking for the types of products you sell. Are your pages coming up? If yes, then good start. If no, then look deepter into the SEO strategy and try to understand it. Only you can make the call as to whether this particular SEO guy is getting you the results you need. Read the posts here for a few weeks and you'll have a much better appreciation for SEO: www.seomoz.org/blog