1.)Does medicinal marijuana constitute "intrastate commerce" even if the ladies grow their own marijuana?No, it doesn't. (note, all of the quotes below are found in the court's opinion(s), found
here)Let's take a look at the Supreme Court's test for legitimate exercise of commerce clause authority, shall we? From the majority opinion:
QUOTE
Cases decided during that new era, which now spans more than a century, have identified three general categories of regulation in which Congress is authorized to engage under its commerce power. First, Congress can regulate the channels of interstate commerce. Perez v. United States, 402 U. S. 146, 150 (1971). Second, Congress has authority to regulate and protect the instrumentalities of interstate commerce, and persons or things in interstate commerce. Ibid. Third, Congress has the power to regulate activities that substantially affect interstate commerce. Ibid.; NLRB v. Jones & Laughlin Steel Corp., 301 U. S. 1, 37 (1937). Only the third category is implicated in the case at hand. (p.13)(emphasis mine)
At first glance, it seems absurd that six cannabis plants that are grown for individual consumption would potentially have any effect on interstate commerce, much less a substantial one. Justice O'Connor in fact makes this very argument in the dissent, arguing, "There is simply no evidence that homegrown medicinal marijuana users constitute, in the aggregate, a sizable enough class to have a discernable, let alone substantial, impact on the national illicit drug market or otherwise to threaten the CSA regime." (p.12) Justice Stevens apparently disagrees. The precedent he relies on is
Wickard v. Filburn (1942), In the case of Wickard, the defendant was growing too much wheat under Federal quotas, even though the excessive amount produced was specified for his personal consumption. The court found "even if appellees activity be local and though it may not be regarded as commerce, it may still, whatever its nature, be reached by Congress if it exerts a
substantial economic effect on interstate commerce." (p14) (emphasis mine)
Bearing that in mind, one would think that Angel Raich's gardening efforts would hardly constitute a substantial economic effect, especially if she had no intention of selling it, right? Wrong. The Wickard application gets even worse. This guy is a farmer by trade, Angel is not. Also, a portion of his crops were designated for interstate commerce, Angel's were not. Finally, the aggregate excess of wheat from Wickard's farm (and others if they violated the quota) had the ability to significantly impact market prices for wheat. Can the aggregation of the unsold pot for personal medicinal consumption in California do the same?
Additionally, the respondents argued that their specific activities were not "an essential part of a larger regulatory scheme because they had been isolated by the State of California, and [are] policed by the State of California, and thus remain entirely separated from the market. "(p27) This was the core of the finding from the appellate court, arguing that the California law placed this activity in a special class that would effectively remove it from any potential commerce exercise and thus would not be subject to enforcement of the CSA. Some might argue this to be a valid exercise of state police power.

Stevens obviously disagrees, but I find nothing in his analysis successfully making this any commerce exercise, potential or otherwise.
2.)Should the 10th amendment figure into this case at all?Absolutely. This precedent has the potential to obliterate any concept of federalism. Justice O'Connor, in the dissent, agrees:
QUOTE
One of federalisms chief virtues, of course, is that it promotes innovation by allowing for the possibility that a single courageous State may, if its citizens choose, serve as a laboratory; and try novel social and economic experiments without risk to the rest of the country. New State Ice Co. v. Liebmann, 285 U. S. 262, 311 (1932) (Brandeis, J., dissenting).
Is there a better example of the state acting as a "laboratory" than giving its citizens a very specific right to use a controlled substance and regulate its use?
To show you what strange bedfellows this case made, I found Justice Clarence Thomas' opinion particularly poignant:
QUOTE
If the Federal Government can regulate growing a half-dozen cannabis plants for personal consumption (not because it is interstate commerce, but because it is inextricably bound up with interstate commerce), then Congress Article I powers as expanded by the Necessary and Proper Clause have no meaningful limits. Whether Congress aims at the possession of drugs, guns, or any number of other items, it may continue to appropria[te] state police powers under the guise of regulating commerce. (p.9) (emphasis mine)
His definition of what actually constituted commerce was also pretty convincing:
QUOTE
Throughout founding-era dictionaries, Madison's notes from the Constitutional Convention, The Federalist Papers, and the ratification debates, the term commerce is consistently used to mean trade or exchange - not all economic or gainful activity that has some attenuated connection to trade or exchange. (p.2)
3.)How does the actions of these two ladies significantly impact commercial trade if they grow their own marijuana and make their own items used to smoke it?It doesn't, see answer to #1
4.)Is this an anti-state's rights opinion? 
Yes, see answer to #2
Now, arguably if you only use the "commerce" argument as outlined in answer to question #1, there is an invitation for abuse. I mean this would legimate growing poppys in your garden for personal use right? Wrong. What makes this case convincing is that California specifically created a class of use that was consistent with the exemptions offered in the CSA. Specifically, the ability for the controlled substance to have a medical use. Up until now, attempts to get Congress to reclassify cannibis from category I status (no medicinal value) had failed. We can offer a completely separate debate on whether Congress should in fact do this. In fact, Stevens even advocates as such in the close of the majority opinion. Unfortunately, we know what can happen when you rely on Congress to do the "right thing" (note: holding breath not recommended).
I really hope the court is forced to revisit this in 2009 (assuming a Dem wins the white house and we can allow some of the moderates to retire). I will also pray for good health for the remainder of the court, even though ironically Rehnquist sided with the dissent in this case. Strange bedfellows indeed.
edit, fixed a mysterious dangling tag