The xtracycle is dreamy, but a trailer is easier to leave behind when you don't need it. I'm a trailer lover, so I'll offer up a few thoughts on trailers:

• B.O.B trailer is easy to pull, low risk of hitting something, but requires a special skewer which can be a problem sharing with multiple bikes or with a solid rear axle (i.e. internal hub).
• Burley and similar kid trailers are easy to pull, hold more weight than you'd guess, and can be found second-hand pretty easily, but have more aero drag at speed and protrude significantly to the left of your bike tire line. Burley makes a low profile, cargo only version that is pretty extensible. A sheet of plywood and/or rubbermaid action packers are good mods to any dept store version of these trailers.
• IMO, trailers that attach to the seatpost affect the handling of the bike with any significant weight in them. You can correct for it, but trailers that attach to the axle or stays don't affect handling as noticably.
• Finally, as a cabinet maker, you probably have good access to "scrap" materials. Ever consider building one?