Hi Gene,
Electrical systems are sort of like anchors in that they can spark arguments among sailors dominated by an almost religious fervor. In my (not so humble) opinion, the setup you describe is the ideal one for most boats. It eliminates the possibility of running down your starter battery by leaving the radar on or something like that and the combiner eliminates the possibility of your forgetting to throw an A/B switch and leaving a battery uncharged. I like the combiners that S/V Yandina sells (http://www.yandina.com/NewCatalog.htm) and am now on my third boat using them.

On my boat, I have two huge, 700AH house banks, each consisting of 6 golf cart batteries, wired into the boat through an A/B switch and connected together with one combiner. I then have another pair of the golf cart batteries as the starter battery and also connected to the house banks with a combiner. I recognise that this is massive overkill for most boats (I'd be happy to discuss the reasons behind my decisions if anyone is interested).

If I had a smaller boat again that was primarily used as a day sailor with some weekend or longer trips, I'd have it set up with the 2 group 27 batteries wired in parallel (some will argue this point) to one side of the A/B switch and a separate starter battery wired to the other side.

NOTE: When setting up a system with combiners. you don't want to mix battery types, for instance, a wet cell starting battery and a gel cell or AGM house battery. Ideally, they should all be of the same brand and model, but if they are at least of the same kind that's generally good enough.