I use my bandsaw almost predominantly for ripping solid timber. With that in mind, I tend to keep it fitted with the widest blade that the saw can adequately tension (in many cases, this is one size below the manufacturer's specification - eg. ½in instead of 5/8in).
But, you can get perfectly parallel cuts with a good quality ½in wide blade, provided it is set correctly. I generally use a ¾in blade for ripping, even though my bandsaw will take blades up to 1¼in. 4tpi seems to work well for general stuff (timber no more than 2in thick and bits of 18mm MDF) but, for anything deeper, I either use a 3tpi blade or one of Ian's awesome Supertuff Fastcut blades, which give an unbelievable finish while sharp.
In an ideal world though, I'd have an additional smaller saw (and the space!) set up with a narrow blade for cutting curves and shaped work.