While I downloaded the Service Pack 1 for VS2008 from MSDN shortly after it was made available, I still have not installed it.

I have been watching a variety of email lists and blogs where many very smart people are having quite a bit of trouble with the install.

There are also many who have had a perfectly smooth trouble free installation.

But I'm waiting until I have time to deal with the worst, just in case, before I begin.

So my advice to you is not to just go for it but look around to see what folks who are starting with the same set up as you have been experiencing and choose the right path for your scenario.

One trend I have noticed is that people who have the cleanest installations of Visual Studio 2008 RTM have the least amount of troubles. It's those of us who have been playing with Betas and other interim bits that are suffering the most.

Choose the right download
There is an ISO available to download but the smaller installation will actually go back to the web to stream down bits and pieces as needed. So if you are planning to be off line when you install, you'll want the ISO.

Here's a blog post from Heath Stewart, VS install guru at Microsoft that you should check before running the installer that depends on the web:

ISA Proxy Client may be required to download VS 2008 SP1

Preparation Tool to clean up interim bits

There is a preparation tool that you will be pointed to if you attempt to install the service pack on top of other interim bits. That is to help clean up your computer and return Visual Studio to it's RTM state prior to applying the Service Pack.

Another post from Heath on removing the previous bits: 2008 SP1 Beta must be removed prior to installing the release of VS 2008 SP1

At the bottom of that post, Heath says that you don't need to do this for the Express versions.

Have your RTM Install disc available

The preparation tool requires that you have your RTM install disk on hand. If like many, you installed from an ISO file, not a DVD, then you'll want to have that file mounted on your Virtual DVD before you get started (e.g. Daemon Tools).

Some folks who are installing from a clean RTM have reported that they have also been asked for the installatoin disc so be prepared for that, just in case.

Silverlight 2.0 Developers

There's a refresh of Silverlight Beta2 Tools for Visual Studio. See Amy Dullard's blog post for info on the refresh and when you should apply it relative to applying the Service Pack.

SQL Server 2008 Users

Install the service pack first. SQL Server's installation  looks for the SP1 bits on your machine. I have seen people say that the installer has still been confused even if the SP1 was already there so you might want to do a little research on this too.

Read the installation notes

Set aside some time.

I've seen reports of successful installs that took anywhere from 45 minutes to over 2 hours.

Set aside some hard drive space

This is a big complaint from people that the install requires a lot of free space. Here's Heath, yet again. on why installers require so much hard drive space.

Let me know how it goes

Maybe you'll give me the confidence to try it myself. I'll have to do it soon because I need to update my book to reflect the RTM bits.

With the prevalence of betas and previews and so many combinations of these that we may have on our computers, it's a huge task to create an installation that can handle any scenario. This is why we're supposed to use virtual machines when testing betas. But I have the Service Pack 1 Beta installed directly on both of my development machines because I got sick of using a VPC. SO I can't complain if my update doesn't go smoothly. I just need to be prepared for whatever happens and to spend whatever time it takes to resolve it.

Who knows, mine may just go smoothly like many others have. I'll definitely let you know!

Update: Success! See my update.