Recently went to Islay for a week and thought I'd do a bit of a trip report, hope its of use for people considering a trip up there.
I spent a week, stayed at the Port Charlotte hostel, which is a cracking spot and would certainly recommend. I spent the week using buses and hitchhiking, which was really easy and certainly not having a car was not a loss.
I managed to visit 7 of the 8 distilleries, and did no more than 2 in a day, and even that was a struggle at times, as you can easily lose yourself in the amount of different malts you have (you lose track of them in your head, so wouldnt certainly recommend writing tasting notes as you go, not as scoring/publishing thing, simply to keep track so when you look back you remember them all.
In terms of the distilleries themselves
Bruichladdich - Only did the basic tour, which meant tasting only the new 10 year old, but kind shop staff offered us Port Charlotte PC9, and a 19 year old which was being bottled in the shop (it was a bottle your own from the cask, which offered a certain novelty). Overall it was one of the better tours, in terms a really good level of understanding from the guide, a smallish group and a slow enough pace. The shop was well stocked compared to others on the island (admittedly they have 10x the range of most others but the staff were well informed and gave a helpful understanding). Definitely worth a visit (if you are staying in Port Charlotte I'd recommend walking it, though its a straight road its a lovely walk)
Bunnahbhain - I did the £15 tasting tour, which gave 4 expressions, it was a less polished tour than Bruichladdich, with a must smaller shop. Whilst the tasting was ok, I couldnt help but feel rushed. The signs of the distillery emphasis on blends were clear to see. On the plus side, its a lovely walk from the Bridgend to Port Askaig road (about 1 1/2 hour walk down a lane) and if you want to stretch your legs its a nice distillery to visit (I hitched one way and walk back via Caol Ila)
Caol Ila - Is currently shut, I walked down the hill as far as to be able to see it. Obviously with the Diageo connection you can try plenty at Lagavulin (and they could recommend Caol Ila there)
Kilchoman - Not the easiest to reach if you arent driving, but definitely worth a visit. I hitched both way from the main road (about 5 miles). The distillery obviously has the attraction of its own maltings, but more than that, its probably the most welcoming of all the distilleries and even on the normal tour allowed a proper tasting of 2 expressions (the new 100% Islay and the Winter 2010 release (the Spring 2011 was sold out)). In addition to the distillery, a couple of attractions for those with a limited time are a cracking cafe to eat! And for those non whisky moments, a stunning beach at Machir Bay about a mile walk from the distillery. Its definitely worth allowing some extra time to head down for a walk.
Lagavulin - Did the warehouse bit of Warehouse demonstration (having arrived a bit late for the tour). Walked from Port Ellen, which was a nice idea as its an easy couple of miles to stretch your legs. The demonstration itself is basically a tasting from casks in the warehouse of different ages of Lagavulin. Certainly informative as a talk, whether its worth your money is whether you have a taste for Lagavulin tbh, it didnt blow me away, but then I suspect that was much to do the whisky being tasted as anything.
Laphraig - The most interesting of the tours, and a snip at £3, by far and away the most informative, obviously with their own maltings, its something they emphasis on, with very friendly staff. The tour itself gave a tasting of the Quarter Cask, which, considering it was a standard tour I was pleased by. Though I only did the standard tour at Bruichladdich and Laphraig I noticed most places only gave their most standard bottling for taste. They gave the 10 year old and 18 year old to taste against, which I think was important. I'm far from a Laphroaig drinker, but I would certainly recommend it as a tour if you have limited time
Ardbeg - I did the tasting tour as the afternoon of double day with Laphroig in the morning (which works excellently in terms of time, if you do the morning basic tour at Laphroig, you have plenty of time to walk along to Ardbeg, lunch in the excellent cafe and then time for the tour and then time for a wander before the bus). The tasting tour, is in essence a standard tour, then you try 5 expressions, and as a tasting goes it was one of the better ones (with right level of advice/pointers with a willingness to discuss your own views. The 5 expressions (Blasda, 10 year old, Uigiedeal, Corryvreckan and Alligator) were tasted in a good order (as above), and not just in age like some places.
Bowmore - As I'm a Bowmore drinker, I thought I'd go for the Craftsmen tour, this is basically a personal tour, with as much time taken as you'd like, a tasting from casks in the warehouse and then up to the bar for your choice from the range (including some of limited editions (Maltmens and Feis Ile 2009 were amongst the 15 choices). Whether its worth the £40 price, is debatable, as I am a great Bowmore drinker, I think it was probably worth the price to have a personal tour, which obviously allowed far more discussion than on a normal tour, then to have the choice in the bar (with recommendations) is nice, especially if you are familiar with core range. Others, who arent Bowmore drinkers would probably stick to the normal tour and be happy
I would certainly urge any one going to take time, I did no more than 2 in a day (Lagavulin/Bowmore and Laphroag/Ardbeg), and having a week allowed me to spend a bit of time exploring the rest of the island. Public transport is very easy and practical, and gets you out and speaking to people, on an immensely friendly island. Have no fear if you miss a bus, I found hitching is easy (though as always everyone has to understand the risk), and even when I was standing at bus stops people stopped and offered me lifts. As a base, Port Charlotte was excellent, easy enough with public transport and a couple of good places to eat, mention of the Port Charlotte Hotel, with an excellent whisky.
Hope thats of help to people, any questions give me a shout