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.
Love bandsaws! I have 2 favourites. One close to max width, exactly as Olly says (i.e. close to the max the machine is rated to take, but not the max as they often struggle to tension on the limit). Tooth count depends on thickness of course and we have to compromise. I go for about 4-5, and on thicker stock I just get patient, I mean feed a tads slower. And my second which I rave about is a 'meat & fish' blade - very thin steel, so fine kerf. Brilliant for more precise work, veneers etc. I was also very surprised to see how long they last. I truly love those blades, but need a basic tough rip blade for general work too.
I got the axminster 450n bandsaw this year, it goes to 1 1/4" but satisfied with a 3/4" blade from Ian.
However I have started using my old jig saw instead of a 1/4" blade for my tissue boxes because it saves changing blades and the set up business which can take a few minutes if its then going back to a larger blade again later in the day etc.