Whenever you decide to ride this (I have done it several times) check CalTrans road conditions
http://www.dot.ca.gov/cgi-bin/roads.cgi. I-80 is being completely redone from Newcastle to the state line over the next few years. There could be portions of it that are reduced to one lane with no shoulder for bikes. Lane blockages can happen with very short notice, so it would be best to drive I-80 from Baxter to Cisco Grove exit (20 miles) and check out the safety aspect of your ride just before you do it. You can also pull over and check with the construction crew to see if they are planning to restrict the lanes on the day you are planning to do the ride. Also check out the amount of stuff on the shoulder. Last time I rode it, there was a lot of metal parts that had fallen off the vehicles and the shoulder was pretty littered.
It is a fun ride. The climb out of Baxter is not bad. The trucks are in the right lane and are generally moving very slow, so they provide good blocking from the faster cars. The downhill from Nyack is pretty fast, as is the stretch from the Grass Valley exit to Cisco Grove. Cisco to Donner Lake is on Historic Highway 40, so the traffic is light. The climb from Rainbow Rd. to the top of Donner is about 1500' of 5-8% grade. The 3 mile downhill from Donner Summit is a blast, but be careful gaining too much speed, unless you know the road very well. The first sweeping right over the rainbow bridge comes up really fast and is a tight turn. There are several decreasing radius turns which will scare you if you come into them too hot. Also, be prepared for crosswinds as you head across the lower part of the descent.