I am a big fan of the Quad Tip fly lines from SA. I have 2. One on my 6 wt and i on the 7 wt.

You get a floating tip, 2 different sink tips (1 fast, one slower) and an intermediate tip. I use the Intermediate tip alot for Smallmouth. They dont cast bad at all. A lot better than the loop-on 5 ft sink tips. The loop to loop connections work fine. They go through the guides reasonablly well though it helps to pay attention where the connection is while fishing. I just lower the rod tip a little and the connection goes in or out of the guides very easily. If conditions change or you need a different tip, it's changed out pretty quickly. Just un-loop the old one and loop on the new one. Tie a fly back on and you are good to go. I keep leaders on each of tips so the leader gets changed out with the tip each time. Short learders on the sinking tips and longer leaders on the floating and intermediate tips.

-wayne