What are you worried about specifically? I’m running three servers with ESXi (using the VMware Essentials package that retails for $999 and sells on the street for about $750, it adds a vCenter Server license so you can manage up to three servers from a single interface) and have been for over a year. It’s excellent, but keep in mind with only one server and no SAN you can potentially end up with “too many eggs in one basket” if your ESXi server fails without a second ready to take its place that has access to the virtual machines. If that one server dies, it takes all the servers on it down until it’s back up. That would be the only “gotcha” I’d be aware of. It’s one reason why I have a SAN and at least two servers–should one server die, the other can run all of the VMs they were previously sharing, achieving better uptime (and cost savings since I’m running 23 VMs on primarily two servers) than spreading things out on physical hardware for every server. But you need to get to shared storage plus two servers before you get some of those benefits.

However, even one ESXi box can work really well as long as you keep the limitations in mind and have backup plans, and enough tolerance to survive for a while if the box is down.

We have windows server 2003 and I would like to upgrade to 2008. I was going to move it to a box with a xeon 5130 chip.

I am just a little worried about using VMware’s ESXi