I've blown my proverbial load on Enterprise, and while I appreciate the money to be made, I've found that my psyche is more suited to 100 small wins than one win worth 100x the others. In short, enterprise isn't for me, at least, not if I'm involved in the sales process. The sheer arbitrary-ness of it was so mentally exhausting that it affected my productivity.
I can work on enterprise software, but if I'm in any way involved with the sales channel, it's a hardship.
For me, the happy middle ground is vanilla B2B, e.g., the same general demographic that 37Signals sells to. You still have customers that want to pay you money, but while cost is a factor, it isn't usually the driving factor -- there's likely little difference between $25 a month and $125 a month, assuming you're solving a problem that isn't cost-centric, and you're saved from the mental turmoil of enterprise whale-hunting.
We haven't ruled out enterprise but I hope and imagine that our sweet spot is B2B.
As you said it has much of the benefits of consumers (little friction to get in the door) and enterprise (willing to pay).
There are two things about the change which are very refreshing.
First, we're talking with people who want to pay us money and the amount doesn't even really matter. We're priced 10-100x over what we were charging consumers.
Second, the support overhead of supporting a crapton of free uses has dwindled and we're now able to provide significantly better support to paying business customers. We do phone support even.
All I've ever done in the past have been consumer startups. I don't think I'd ever do one again.
Edit: It's no silver bullet by any means. But it just feels much saner than the homerun derby which is the consumer Internet.