Hi Daniel, welcome to the forum and a BIG congrats on getting your SP3!! If you haven't been lurking here already, you'll find this place full of knowledgeable folks and tons of info.
Regarding Complete- I would totally go for it. I have it myself (and had it on my SP1) and would absolutely consider it a "must-have" purchase for the SP3.
The only other option that I personally would use is Square Trade. They used to be a tad bit more than Complete, but now it looks like they've revised their prices.
Complete is $149, which gives you 2 years of accidental damage, and 2 years of Help Desk tech support. You can have up to 2 instances of damage (getting your SP3 replaced) and each time costs you $79.
Square Trade is $139 up front, 2 instances, and $79 each instance. With Square Trade, you have to send in your SP3 and wait for them to send it (or a refurbished one) back.
Microsoft will allow you to do a "rapid exchange" where you agree to let them put a $1000 hold on your credit card, they immediately send you a new (or refurbed) SP3, and when you receive it, you send your defective one back in the box the new one came in. Once they receive the defective one, they release the hold on your CC.
My advice is to go with Complete. The few extra dollars compared to Square Trade is well worth the extra tech support and that fact that you're dealing with Microsoft directly for an exchange.
Hope it helps!