In 1994 we purchased a new 27' 5th with 1 slide. It was problematic because it had a cable system with a electric that moved it in/out. Cables were always needing adjusting.
In 1997 we traded for a new 36' 5th wheel with three slideouts which were rack/pinion electric motor driven. No problems at all.
In August 2002 we traded for a 2003 36' Gulf Stream Yellowstone Diesel Pusher with two slides, L/R was hydraulic and bedroom slide was electric. No problems at all with operation or leaks.
In Sept. 2004 we purchased our 40' Gulf Stream
with four slides. Two of them are hydraulic (Power Gear) and two of them are electric. We haven't had any problems with any of them.
The early slide outs in some manufactures did have problems, but I believe most of them have been eliminated. At least the ones we have owned since 1997 have been.