MGG is a good GP to own, good management, conservative strategy, solid assets, low risk assets..the only knock has been that many question how much growth can you squeeze out of refined petroleum lines? I think mlpfollower can add more on MGG than I bring to the table. I think he has looked into gasoline and refined products consumption growth patterns..I may be wrong, but recall it being around 1% to 5% a year. So, unless you have pricing power, internal growth might be a little slower than some, but they have a large coverage ratio from what I remember, so that is good.
I also would point you in the direction of NRGP and MWP. NRGP is largely propane, but they have made a grand effort to diversify out of that field into gas storage and midstream. Again, good company good management, good leverage on NRGY's growth.
MWP - where do I begin. A real dilemma. These guys have some very very good assets, especially the recently purchased Javelina gas processing plant(not E&P processing but refinery off-gas) and the Carthage processing plant. Superb leverage, no debt, but the kicker is that management is pathetic. That being said, it is still one of my largest holdings because it is selling at a price that is crazy cheap, especially considering they just wrapped up some much needed financing that got them out of hot water. They ought to be able to grow the distribution from $3.48 to $4.00 over the next 4 Q's, which should allow MWP to double its dividend from $.70 to $1.40 (I have posted much of the math behind those numbers on the MWP board-but also be forewarned that I have been very critical of management- especially when it comes to disclosure).