I've added iPad support to v222 of Umbrella and TinyTSS. As the device isn't out yet, I cannot be 100% certain it works perfectly. I'm confident it'll work just fine though. From what George Hotz posted on his blog, I have high hopes for a quick jailbreak for 3.2 (untethered). That jailbreak will make Umbrella and TinyTSS very important for early adopters of iPads with OS version 3.2.
Edit: I've gotten quite a few reports of folks not being able to point to 'Saurik - Cydia' and obtain their shsh. Check your etc/hosts file having an entry in that file for gs.apple.com will cause your issue. Make sure that entry is commented out by putting # at the beginning of the line with gs.apple.com.
Edit: Ok guys, a couple notes. Yes your SHSH will be different each time you run it for 3.1.3. If you did a little bit of reading of my previous posts you would have noticed my mention of APTicket in the SHSHs for 3.1.3. This is a unique value for each SHSH request. So far iTunes doesn't use it yet (to my knowledge). This is why it is VITAL that you do NOT update iTunes past 9.1. (In my personal opinion I would have a version 9.0.2 lying around because that is what I use).
Future versions of iTunes can use this value to further [in]validate your local restore. This will eventually require an iTunes patch to do local restores. And then, when the new bootrom comes along, they can move the [in]validation based on the APTicket to the device and then anyone with THAT new bootrom will be really screwed.
Edit: Please do not direct link the download. I want the download and the hashes to appear together. Thank you for your understanding.
fw-umbrella-semaphore-222.zip md5: d17e449ba79c1c1caa4c0a6dd970eb0e
fw-umbrella-semaphore-222.zip sha1: 6c2229d615e40560f0d67fec5649192dd35f6461
umbrella.exe md5: b667ec438182bc6771e420ddbc657002
umbrella.exe sha1: 2408764b7b2d8b7ea80f6bf23d9044658d5dabbd
tinytss.exe md5: 35d4e41775fe7741bc48da8dff374bd4
tinytss.exe sha1: a383bb72f7cb6b5058a5c1b4568bbef672a533ae
umbrella64.exe md5: 31f0ce296d28a00b05b2fa82cde83a45
umbrella64.exe sha1: cf5dabd9e03c349158e220047b32b5fc07227d18
tinytss64.exe md5: aeeeae6bdd85343d8b4438f2d0edcc76
tinytss64.exe sha1: f5d9355a067a888fcffb76a5e5238848a40e9c57
Umbrella.dmg md5: 018b29a3662bc2c9b55ed93fe32d95a6
Umbrella.dmg sha1: a071492b0417ce2b2926b8df015f7f9c99412365