We climbed Kinabalu in August and thoroughly enjoyed the experience. Having some climbing and mountaineering experience in Europe, this was our first plus 3000m.
We would recommend this to anyone seeking a physical challenge or looking to train for a Himalayan or Alpine expedition.

Physical Requirements
Most people will not suffer any severe adverse affects from climbing up to Laban Rata or to the 4100m summit however it is likely that you may experience some headaches, dizziness or mild sickness. The easiest way to avoid this is to take Aspirin, at the recommended frequencies, from approximately 24 hours before hand until the end of the walk. Make sure you take it with you for severe headaches, especially for the summit push.

The steps up to Laban Rata make the first day tough going on the thighs. Be prepared to struggle up the last 2km unless you are used to this sort of activity. High fitness levels will help but unless you have particularly strong thighs (cyclists, skiers, serious walkers) your lungs may be fine but your legs will struggle.
I found that I was rarely out of breath but that the muscle tear on my legs was quite painful at times. By the time we reached Laban Rata, they were quite wobbly – but fine after a rest.
The summit climb is tough mainly because of the early start – 1:30 am. If you can get over the first tough hour, the rest of the climb will be fairly easy going as it flattens out near the top.

My advice would be to get to LR as early as you can and ensure your legs get ample rest. Taking it slow may seem like the right thing to do at the time but it really just increases the stress on your legs in the long run. We arrived early around 11:30am, had a shower and a few cups of tea before we ventured out to look at he view. By 6pm we were well rested but some groups were only just arriving – leaving far less recovery time.

Coming down can be tough, especially towards the end of the descent. Although its mainly downhill, the second day is by far the toughest, in terms of distance covered (11.4km v 6kn) and the pain you will feel over the next few days is from controlling your speed going down, not climbing up.
Take a pole as it will reduce the strain on your forward leg and take plenty of breaks. Stumbling down on tired legs is one of the only potential dangers of this climb.

Kit
The temptation is to take a lot of ‘just in case’ provisions on a climb like this but your shoulders wont thank you on the way up if you over pack.
Laban Rata is warm enough to not need a sleeping bag – we lugged up Alpine bags and regretted it, as they were just too hot.

Wear on way up:
Light walking pants/shorts
Coolmax t-shirt/vest – it’s a comfy 20 degrees most of the way
Light fleece – you might need this higher up
Trekking boots/shoes – waterproof

Pack:
Water – 2litres is enough as you can buy at LR for the next day
Water reservoir – little sips as you climb are easier to manage than getting out a bottle
Light waterproof jacket
Change of t-shirt for LR
Thermal Top and Pants (it was less than freezing on summit and you wont be able to hang around unless you are wearing base layers)
Hat
Gloves
Spare socks
Headtorch & Batteries
Silk sleeping bag inner – this will protect you against any bed bugs at LR and can be easily washed
Some Hot chocolate sachets - tea and coffee is available bit nothing else
Snacks – melt and squash-proof.
Poles – for way down – they wont help on the way up
Camera etc etc
First Aid – Asprin, plasters and rehydration salts will do.

We didn’t take a change of clothes and went down and up in the same kit to save weight.

What you wont need:
Sleeping bag – too hot
Water purification system – bottled water is available at LR
Spare shoes
Your packed lunch from the Park – it’s a stupid shape and not designed for walking. Ditch it, take your own snacks and buy some hot noodles when you get up there.

Accommodation
LR provides everything you will need for your short stay. The food is OK and will keep you going for a few hours. There are plenty of snacks and drinks to buy.
Rooms are surprisingly comfortable with decent bunks, blankets, toilets and showers.
The view is amazing and well worth any hardships you might have to put up with.

Enjoy!

The climb is the toughest physical challenge i ever experience in my life! The terrain you are walking on varies from wooden planks, muds, rocks to boulders. My team took around 5-6hrs to reach Laban Rata (the only accomodation in the mid mountain). It took another 2-3hrs hike to the summit starting in the middle of the night.
Tough? Definitely no doubt about it but it is achievable.
Once you reach the summit and the gorgeous sight of KK greets you, you will feel that your effort and sweat are worth it.
Recommend to do lots of stairs climbing as training for the climb. Enjoy!

Very expensive just to climb a mountain for 2 days. Just a word of warning, I am of medium fitness and couldn't move on days 3-7. My husband is very fit and was also sore for that long.

Don't think this is a walk in the park, prepare for the walk uphill and down. Both are really hard.

I took 6 hrs to get up (in torrential rain) and 5 to come down (down was also in torrential rain, but easier for me using the handrails). Half the people staying in our hut didn't make it to the summit. Too tired.

We also passed many girls who said they cried or were close to it (including me)

Saying all that, the view is fantastic. The climb down with mountain torq was also fantastic.

Only do it if climbing mountains is ur thing.

I would not do this again.
I would only recommend this if ur prepared.