You will love it Basecurve. Heaps of places to rent boards but if you just rock up it can be quite expensive particularly with the dollar the way it is. If you can take your paddle do it - or buy one there, they are much cheaper than here.
Kanaha Kai www.kanahakai.com have Starboard but not a huge range unless things have changed since last year but they will do a deal if you book ahead - just e-mail them to see whether they have anything newer than the 12'6 and 12'2.
(just checked the site and they list 11-2 and 10-5!!) They are great to deal with as well.
Hi-Tech and Hawaiian Island also have heaps of SUP gear but in my experience very expensive to rent from (maybe the recession has fixed that!)
Pono Bill certainly worth talking to and also Giampaolo Cammarota who is a friend of mine that sometimes has really good contacts for accommodation and gear, knows everyone and is a fantastic guy that you can trust - here is his blog site
mauisurfreport.com. Giampaolo and also the guys at Kanaha Kai will tell you what is working everyday too.
You can really luck out on swell and wind in Maui but whatever you get it's a life changing experience! PM me if you want any more info.