The most important thing you can talk about is what you know best--your own personal story about how e-cigs have helped you.
You can also say that you are concerned that there are groups that would like to see the product banned, and you hope that he will help keep the products available, effective, and affordable.
The FDA did its best to shut down the e-cigarette industry back in 2008 and 2009 when it began seizing shipments of products coming in from China, claiming that the e-cigarette was an unapproved drug-drug delivery device combination. After a legal battle in the Federal Court system, the FDA backed off on banning, but has announced that it wants to "regulate" e-cigarettes under the tobacco act (Family Smoking Prevention and Tobacco Control Act, signed into law in 2009). The problem with that is if they implement the exact terms of the law (which were written with combustible cigarettes in mind), they could ban the sale of any product that entered the market after February of 2007. There is a provision that allowed tobacco companies to apply for "substantial equivalency" status. The company would need to prove that the new product is nearly exactly the same as the ones marketed prior to Feb. 2007. Unfortunately, there was a deadline for submitting these requests built into the law, and it has already passed.
There is also concern that even if the FDA didn't move to shut down most of the business as described above, that they would apply unreasonable regulations that would be impossible for most companies to follow. They might impose regulations that would make the products less effective as an acceptable substitute for smoking, such as setting the maximum % of nicotine too low or outlawing all except for tobacco flavors.
Then there is the problem of the tobacco company user fees, which were based on multi-billion dollar corporations like RJ Reynolds. Nearly all of the vendors that participate in this Forum could by no means afford those fees.
Those are our worries at the Federal level. At the state level we have to keep fighting legislation proposed by the groups we refer to as the Anti-Nicotine and Tobacco Zealots (ANTZ). These include the Americans for Nonsmokers' Rights, Action on Smoking and Health, American Lung Association, American Cancer Society, Campaign for Tobacco-Free Kids, etc. For a while, they were proposing outlawing all sales, then it became a ban on indoor use (by including the use of E-cigs in the definition of smoking), and some have even suggested taxation.