Maintainence is no problem as the fundamental parts are common for other engines. Tune up parts are very available and relatively inexpensive. Even other items like gaskets or bolt ons (water pump, starter, alternator) are as available as the small stuff. Broadly speaking, I feel it's an engine easier to work on than a small block Chevy (dist in front, plugs above manifold, external oil pump, etc).
No problems doing maintenance - it's a Caddy, nothing ever breaks!
I'm kidding of course.
But, the big tune-up parts, distributor and carburetor use parts shared across basically the entire GM line. Internally, the distributor is the same as that used on Chevy V8's (both big and small block) and is probably common with the distributors on other GM brands. The Q-jet was used on V8's across basically every GM line, so rebuild kits are common and readily available. Brake pads are the same - the same pads used on fullsize GM cars and trucks from '69 untill sometime in the 90's.
Ain't parts interchangability great! Eli Whitney would be proud!
I also agree with 472 about it being easy to work on. Everything you need to get to is out there and reachable. Even the oil filter isn't hard to get to. Of course, with the acerage available under the hood...