It seems that when I designate relievers as a lefty or righty specialist, it is very rare that they ever get used. I'm just curious what veteran SimLeague Baseball players think about their experiences using lefty or righty relief specialists.  Is it worth using these roles?  Perhaps these roles are more worthwhile in higher salary cap leagues.  But in leagues with a $100 million cap or less, lefty and righty specialists don't seem to do anything.    

I've had them used a lot, and they have gotten killed. Mostly a LH with a pitch count of 5/10, pull 5....and he still got smoked.  Im waiting to see it work,

You know, I've noticed that trend in Live play.  Also, I've noticed that lefty/righty matchups don't seem to mean squat in SimLeague.  My right handed hitters have better averages against righty hitters and my lefty hitters do better against lefty pitchers.  Doesn't make a lot of sense. 

I've only designated a specialist a couple times. they rarely got used so I stopped using that designation.
Sparky considers matcups when choosing among several RPs so it helps to have both L and R pitchers with the same designation.

I wouldn't use a pitcher with more than 40IP in that role. Also if the total number of relievers in your pen is low, I might not use that setting as it causes more appearance fatigue.
I'm not familiar with the player "not getting used very often". I don't think I've ever had problems using up their IPs. Thats just my experience though.
As far as effectiveness, its just one of those deals where it doesn't hurt to use them that way. It can only help. If it makes your lefty face 40% lefties instead of just 28%, then you've helped yourself some. Your specialist will almost always come in facing the appropriate matchup. Who the second hitter he faces is, is left up to chance. If you use a 5/5 pitch count with a 5 pull setting, he'll face just the one batter more often or at least come out of the game if he gives up a hit and is in a bad situation.
Also, when looking at a pitcher's stats, don't forget about switch hitters. A lot of people complain that their specialist is facing too many of the opposite handed batters, but switch hitters are always listed as the opposite hand.

Also, "noticing trends in live play" is something I recommend you stop doing immediately. Your eyeballs deceive you. I don't advise new players to play live right away for that very reason. Use your head, not your eyes.

I only run progressives and themes and quite often use LH/RH spec.

Usually they are low ip guys and/or players w/ high oavs, depending on the progressive/theme. I set them at 6th inn, 5/15ip and a 5 pull. Unless they have crazy high  HR or BB #'s, I find they do tend to overperform their RL #'s.

I agree w/ boogerlips' post from 2 above as well.