Check for Network, Then Mount Share (Problem)

I'd do a LaunchAgent (which runs as the user logging in) that calls the script (stored locally on the client).
Have a look at http://macmule.com/2011/09/08/how-to-map-drives-printers-based-on-ad-group-membership-on-osx/ for example.
Also, i prefer using netcat instead of ping for checking the server connection,

nc -z 10.10.78.12 445

or something like that

You can try to define getting the logged in user with an attribute:

currentUser=$(ls -l /dev/console | awk '{ print $3 }')

and use that to have it not run as root, or at least apply to the current logged in user.

Echoing @Chris' statement about using a local LaunchAgent for this. As that will run as the user you won't need to worry about getting the logged in user and forcing root to run the command as that user.
Also, its just my personal opinion, but anytime we need something to run at every login, we look in the direction of a LaunchAgent and script, or calling an app rather than having an ongoing policy run at login. Although you lose out on logging (unless your laucnhd also creates logs which is possible), its generally a better.

This is actually what we do. We created an Applescript based app that checks for the network and then attempts to mount the user's share, or exit if the network isn't available. It gets called by a local LaunchAgent.

Awesome. Thanks, guys. I am aware of the launch agent and looks like I'll be going that direction. Huge help. The second part, though...

If you notice, the script creates a directory and maps the share to it. My logout script disconnects the share and deletes the folder. This doesn't seem like the cleanest way to do this. It appears I've also wiped out the contents of a share with it, even though the rm is programmed to run after the umount.

You might want to look at doing a pure Applescript mount command in the script, rather than doing mount -t smbfs. I'm not sure if this is the exact syntax but I believe it would be something like:

mount volume "smb://sjdfs01.ehi.ehealth.com/" & userName & "$"

The advantage with that is there's no need to create the directory for the mount point up front and then try to clean it up after it unmounts. Its akin to using Connect to Server and mounting it that way.

I agree with @mm2270 and @Chris' posts that LaunchAgents are probably the way to go. Just wanted to offer up an alternative in case you hated LaunchAgents or something ha.

To follow up once more, I would modify your script to look like this (I can't test it of course, but give it a try)

#Wait for full login
delay 10

#Check to see if DFS is available
set IP_address to "10.10.78.12"
set IP_Valid to true
try
    do shell script ("ping -c 2 -o " & IP_address)
on error
    set IP_Valid to false
end try

#Get current user name
set userName to (do shell script "ls -l /dev/console | awk '{print $3}'")
#Mount users share point
mount volume "smb://sjdfs01.ehi.ehealth.com/" & userName & "$"

Note also that I threw the -o flag into the ping line. -o tells ping to exit after the first successful response. So even though its instructed to send 2 pings, if the first replies back successfully, it stops and moves on to the rest of the script.

@mm2270 I originally had a pure AppleScript solution exactly as you have suggested, but it wouldn't run as the user. However, if LaunchAgent will always run as the user, this isn't an issue and I would LOVE the simplicity of it. I will definitely go that route as it "gets two birds stoned at once" so to speak. Thank you all for your help!

@brandonpturner, I have an example that does similar to what you're trying.

http://macmule.com/2011/09/08/how-to-map-drives-printers-based-on-ad-group-membership-on-osx/

By using the mount volume command via an AppleScript app, launched via a launchagent , & setting finder to show connected servers on the desktop (pretty much what @mm2270 said in his last post).

Been working well for us.

@bentoms I looked through there. Nice work!