IMO the only benefit of unique IPs is it makes it harder for SE's, snooping SEOs or competitors to find out too much about your operations, assuming you have private domain registrations.

If someone did a reverse IP lookup on your server would you care if they see all of your other sites?

If the answer is yes, then don't even host them on a single shared server, ask your host to give you different servers per account. This is a good idea anyway because if all your accounts are on a single shared server that does down you're out of business, so spreading them out is to your advantage for other reasons.

Thanks incrediBILL. I also heard that it helps in SEO.

Having a unique IP address also enables you to access your site before DNS changes resolve, and to add subdomains at will.

Jim

I also heard that it helps in SEO

Not that I'm aware of as I've had top ranking sites on shared and dedicated servers.

Heck, even a blog on Blogspot can rank PR5/6 without that much traffic.

It's all about SEO, not about the IP.

I have been told that the location of your IP will effect your SEO performance.
In my case I have got site mytown.ie which is an Irish Community website to be used by Irish people. It is hosted by Host Ireland, which I assumed was in Ireland but yesterday I found when doing a whois on my site that the IP is in the US. Is this going to be bad for my SEO performance, as my site is targeted at Irish people?

For shared hosting, if for some reason other unsavory/spammy type sites are on your same IP you could be affected by them. For example, if you are on the same IP as websites that have been blacklisted by search engines, your website could be affected.

That's where a unique IP address is an advantage.

As for showing up for results related to searches from Ireland, it's best to host your site on a server where the IP address resides in Ireland. Google for example, shows regional results based on IP address and top level domain.