Here are the Slicehost’s advantages:

• Easy provisioning of new or existing slice(system).  Take a couple of minutes to create a new slice.  You can also resize slice’s memory easily(be warned though: the time it takes to get the resize done depends on how many people are ahead of you doing resizing and some other things).
• If you mess up the slice(eg: mess up the network setting so that you can no longer ssh in), you can use the web-based console to get in. When you really mess up your slice, you can drop into rescue mode to fix your slice image.
• You can get private IPs for your slices.  So every bit that transmits between your slices using private IPs is not counted against your bandwidth.
• All your slices’ bandwidth to the outside world is pooled together.
• Slicehost has a API that you can use other services like CloudKick to monitor your slices.
• Slicehost uses Xen-based virtualization which provides better isolation so my neighboor slices in the same physical machine can’t bring my slices down.
• Excellent documentation,  article and tutorial on getting things up and running.
• Active user community(forum, live chat).
• Quick responses on support tickets.  It usually takes less than 10 mins.  Or you can go directly to live chat to ask for an update.
• Last, the most important and useful feature that we can’t ABOSOLUTELY live without: one-click manual/scheduled backups(up to 3 backups per slice), restore a backup to any slice we own.  We have a peace of mind when we know that every slice is backed up on a daily basis.  Second:  When we do upgrades, we can rollback to a backup if the upgrade fails.  Third:  whenever we need a new slice, we can create one based on a backup.  so we don’t need to set up a new slice from scratch.  The backup feature is totally worth the extra charge.

As good as Slicehost is, here are some gotchas:

• Some people argue that Slicehost’s 64-bit systems use more memory than needed.  But I am not going to try another provider without the backup feature.
• As told by Slicehost support:  don’t do OS upgrade on your slices as it’s most likely to break, and Slicehost isn’t going to provide support the upgraded OS.  Your best route is create another slice with the latest OS you want, and load the data on it.  So when you pick a OS for your slice, you should get one with long term support(eg: for Ubuntu, pick the one with LTS).
• Slicehost doesn’t allow you to transfer IP address from one slice to another slice.

Slicehost has become a role model for every hosting provider.