I love smallies on the fly, matter of fact I just chased them yesterday morning on the Lehigh River in JT. Pound for pound, the most exciting flyfishing the average, local angler can expect to find around here. We've floated the Delaware in our inflatable pontoon boats quite abit this summer and we're seeing more on the water fishing this way too. We mostly float a stretch just a few miles upriver of Easton. I got my first flyrod-caught 20" smallie this year.
The key to smallie fishing is definitely weight- you have to get that fly down on the bottom most of the time. We're talking several larger splitshot or a good deal of tungsten putty. Don't be shy you can always take some weight off if it's too much (it rarely is). If you're not hooking bottom from time to time, than you're only catching 1 or 2 of the fish available. My friend is a guide and many times he uses a two-fly system using streamers or buggers: a conehead bugger or muddler trailed by a beadhead woolly bugger, he adds 1-2 splitshot as well in front of the point fly. Also, use shorter leader & tippet sections than you normally would for trout, anything more than a 7.5 foot leader is too long. I usually just use a 4ft braided leader with only 2-3 ft of 3X or 4X tippet or 6lb Maxima. Don't worry much about setting the hook, smallies usually take care of that on their own. Basically just use a strip set for the hookset: as the fish takes just strip in the slack line quickly to put tension on the line, this "sets" the hook for smallies.
The fish are on the feed now and surface poppers can bring big strikes in the large pools & runs on calm evenings. During the day, fish the riffles and tick the fly along the bottom and hold on.
My favorite flies are white clousers, gotchas, and zonkers to mimic shad fry and black or brown woolly buggers and meat whistles to mimic the abundant crayfish and helgrammites.
I could walk down there to the Delaware with just a handful of white clousers and black woolly buggers and have confidence that if the fish are feeding I'll pick up at least a half-dozen smallies without too much trouble... as long as I have enough weight to get the bugger to the bottom! Many times, I've seen weight be the difference between a 3 fish day and a 12 fish day.
Also vary your retreive, sometimes they want the fly stripped in slow and will take it on the pause. Other days they want it stripped fast and will savagely take the fly during a fast strip. Each day can be different, that's fishing.