I have ridden a few recumbents and found them heaps of fun. Ranging from street rockets to full suspension electric MTB versions.
Fun - Absolutely being close to the ground gives you a real sense of speed and they corner like they are on rails.
Maintained - this is an issue, I have ran shops where we serviced them and done a lot of this myself. They don't mount in a stand and therefore require a bit a big bench or you are working off the ground. Also most workshops are fairly small and would struggle catering for them. My suggestion here is seek out a store that is happy to work on them and build a relationship with them. The trick here is they won't really want to store it so by having a good relationship you could arrange same day service.
Parts - Most of the parts are standard - derailleurs, shifters, brakes, bearings, rims, drive chain. When they build them they work around the problems to ensure they use standard kit. Things that are not standard are hubs and sometimes you require tandem cables, but for the most part that is not really and issue.
Why are they not more popular - there are several reasons:
* Stores do not stock them as the floor space v's revenue model does not make sense.
* Consumers struggle to store them at their house.
* As a mode of transport they are really hard for cars to see and, being wider than a bicycle, easier for cars to hit.
* Most work places do not have enough room to store them if you ride to work.
* They do not fit the traditional concept of a Bicycle so people struggle to understand them
let us know how you go..