In the past without virtualization, it normally took several hours to get a new server built, including cabling, racking and OS imaging. Now we can use templates with many OS flavours and we can get a new server running in few minutes.
Currently we are struggling to keep the storage capacity under control and as we do not use thin provisioning our capacity is always a challenge, but the actual used space by the guests is pretty low. We need to find a way to go to thin provisioning and keep that under control and implement automation on the capacity management and have threshold alerting.
I've been using VMware for seven years.
We have no problems deploying vSphere.
So far, I only had problems with stability when we implemented a third-party backup tool that uses VMware snapshots to take backups. It brought some instability to some guests at the beginning and it took us some weeks to get to the root cause and things back to an acceptable level of stability.
This is a very good solution and I work for a company with a global ELA with VMware. But as our contract and all our commercial team is in the US, we have a limited number of vouchers for training and events in Brazil.
The technical support is good and they always provide good suggestions and technical recommendations and the response time for critical problems has always fair been fair.
I have never tried a different server or datacenter virtualization solution before.
I was not a part of the initial set-up or project team. I work on the operations team and I have only been a part of migration team when moving from old versions to newer ones, but I have never had problems.
You should have good capacity management and you might have at least two clusters or more to separate your guests by tiers or have a good notion of resource pools to keep the resource utilization in good shape.
You should understand what is your demand and plan your capacity and resource allocation carefully to avoid double work in the near future.