I just signed up to move up to the Free State hopefully within the year. Looking at the Dover area for work. I'm a mechanical engineer and my fiance is getting her phd in Molecular Biology and Molecular Genetics. We live in New Jersey now and are running for delegates for Ron Paul! She defends this summer so we'll be looking to move as soon as possible. Pretty exiting.
Salem, and the towns around it, are probably your wife's best commuting option to Cambridge, MA. There is a massive bio tech cluster there. I commute down myself. My employer lets me do it off peak hours. So, it takes me about 45 minutes to an hour. I've tried commuting from the Sea Coast and Nashua. I found commuting from the Salem area to be the best option.
Plaistow is a very nice area that's not part of the Salem area. It's across the border in Haverhill and Lawerance, MA are MBTA commuter rail stations. If your wife takes a research position with one of the big pharma companies in Cambridge/Boston and her employer won't let her keep a flexible schedule, the commuter rail may be the best way for her to get to work.
For me, the commuter rail would take about 1:30 minutes of travel each way and would cost more than gas and what I pay for parking. So, I drive. But, had the MBTA been better designed (with express trains, less stations, or a connector line between North and South Station), I'd much rather take it.
You can look at the MBTA routes on their web site: http://mbta.com/
The site has a trip planner and an interactive Google Map overlay of the rail lines on this page: http://mbta.com/schedules_and_maps/rail/
There are also some private bus lines that drop people at the MBTA subway stations: http://www.nh.gov/dot/programs/rideshare/transit.htm
I didn't find those services to be fiscally appealing. But, one of the people I work with takes Concord Coach Lines or Boston Express Bus (I don't recall which) down from Derry, NH everyday.
Finally, there's the DownEaster Amtrak train service that serves the Sea Coast. I never road it. But, I constantly hear about it being in danger of being canceled due to Amtrak running such a large deficit each year.
I'd strongly encourage you to make the move to NH. I think you're really going to like living up here. I personally do. I've turned down many offers to move and work elsewhere. Boston is really the place to work if you're in biotech. I lived in Boston for a few years before I moved to NH. The two places are a night and day difference.